As the eyes of the world remain fixed on Isis, Bashar al-Assad’s forces have killed an estimated 330 civilians in Syria since the start of this year alone, observers claim.

Bombings and chemical attacks like the ones that almost led Britain to war in 2013 have been carried out largely unnoticed as the so-called Islamic State continues its bloody campaign.

Isis has provoked global horror with its filmed beheadings, amputations, crucifixions, massacres and murders, most recently with the burning to death of Jordanian pilot Muath al-Kasaesbeh.

A Jordanian girl holds a poster of pilot Muath al-Kasaesbeh during a candlelit vigil in Amman on Monday (Reuters)

The group’s horrific cruelty to civilians is well-documented, particularly the persecution of religious minorities and anyone who does not conform to their violent interpretation of Sharia law.

But whereas Isis gleefully spreads its gory propaganda videos around the world, the regime’s atrocities including the use of banned barrel bombs and chemical weapons, goes undocumented and unnoticed.

President Assad’s forces are fighting a civil war on several fronts – against Isis, other Islamist militias, secular rebel groups and to quash the anti-government sentiment that started in the 2011 Arab Spring.

A Syrian man carries a girl on a street covered with dust following a air strike by government forces in the northern city of Aleppo

The London-based Syrian Observatory of Human Rights chronicled 127 air raids in just 24 hours earlier this week by regime helicopters and planes.

A spokesperson said Britain, the US and other international leaders that “claim to defend human rights” must work harder to stop crimes against humanity being committed daily in Syria.

“It is a shame on those who pretend to respect the Human Rights to just write and publish statements,” he added.

In pictures: Syria conflict Show all 40 1 /40 In pictures: Syria conflict In pictures: Syria conflict Syria crisis Syrians carry children amid debris following a air strike by government forces in the northern city of Aleppo In pictures: Syria conflict Syria crisis A Syrian man carries a girl on a street covered with dust following a air strike by government forces in the northern city of Aleppo In pictures: Syria conflict Syria crisis Syrians react as they stand amid debris following a air strike by government forces in the northern city of Aleppo In pictures: Syria conflict Syria crisis A Syrian man carries a girl amid debris following a air strike by government forces in the northern city of Aleppo In pictures: Syria conflict Syria crisis An injured Syrian man walks out from the rubble of a destroyed building following a air strike by government forces in the northern city of Aleppo In pictures: Syria conflict Syria crisis A Syrian woman makes her way through debris following a air strike by government forces in the northern city of Aleppo In pictures: Syria conflict Syria crisis People stand on the rubble of collapsed buildings at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad, in the Al-Fardous neighbourhood of Aleppo In pictures: Syria conflict Syria crisis Syrian residents stand amid the rubble of destroyed buildings In pictures: Syria conflict Syria crisis A Syrian resident grasps a mattress amid rubble in the al-Firdous neighborhood of the northern city of Aleppo In pictures: Syria conflict Syria crisis A view taken from Tel al-Sawadi shows a large explosion allegedly at the Wadi Deif Syrian army base in northwestern Idlib on May 14, 2014, which opposition fighters have been trying to capture for more than a year. The Syrian Observatory for Human Rights said Islamist rebels detonated explosives planted in a tunnel under the army base killing or injuring dozens. AFP In pictures: Syria conflict Syria crisis A bullet-riddled parking sign stands amid debris in a deserted street leading into the old city of Homs In pictures: Syria conflict Syria crisis A general view shows abandoned buildings on a deserted square in the old city of Homs after Syrian government forces regained control of rebel-controlled areas In pictures: Syria conflict Syria crisis A military vehicle that belongs to the Free Syrian Army is seen in Al-Amariya district in Aleppo In pictures: Syria conflict Syria crisis A mosque is pictured through shattered glass in the old city of Homs, as rebel fighters withdrew from the city centre in line with a negotiated withdrawal deal with the government after having held out under tight siege for nearly two years In pictures: Syria conflict Syria crisis Buses carrying Free Syrian Army fighters leaving Homs. Exhausted and worn out from a year-long siege, hundreds of Syrian rebels left their last remaining bastions in the heart of the central city of Homs under a cease-fire deal with government forces. The exit of some 1,200 fighters and civilians will mark a de facto end of the rebellion in the battered city, which was one of the first places to rise up against President Bashar Assad's rule, earning it the nickname of "capital of the revolution" In pictures: Syria conflict Syria crisis Syrian government forces hold up a portrait of President Bashar al-Assad (L) while others raise the national flag on top of a pole in the old city of Homs In pictures: Syria conflict Syria crisis Forces loyal to Syria's President Bashar al-Assad run through Aleppo's Bustan al-Qasr crossing after their release by rebels. They were freed as part of a larger deal which saw the last remaining Syrian rebels in central Homs city evacuate their positions and free captives in several locations in northern Syria In pictures: Syria conflict Syria crisis A Syrian woman and two children walk past heavily damaged buildings in the northern city of Aleppo In pictures: Syria conflict Syria crisis A man carries a wounded girl following a reported bombardment with explosive-packed "barrel bombs" by Syrian government forces in the al-Mowasalat neighborhood of the northern Syrian city of Aleppo In pictures: Syria conflict Syria crisis A wounded man sits as he is treated at a makeshift hospital following a reported bombardment with explosive-packed "barrel bombs" by Syrian government forces in the al-Sakhour district of the northern city of Aleppo In pictures: Syria conflict Syria crisis Debris rises in what Free Syrian Army fighters and Islamic rebels said was an operation to strike Al-Sahaba checkpoint, which is considered a gateway to Al-Dayf valley, and remove forces loyal to Syria's President Bashar Al-Assad in Maarat Al-Nouman, Idlib province In pictures: Syria conflict Syria crisis Men try to put out fire at a site hit by what activists said was an air strike by forces loyal to Syria's President Bashar al-Assad in the town of Azaz, north of Aleppo, near the border with Turkey In pictures: Syria conflict Syria crisis Civil Defence members try to put out fire In pictures: Syria conflict Syria crisis Survivors react at a site hit by what activists said was an air strike by forces loyal to Syria's President Bashar al-Assad in the town of Azaz, north of Aleppo, near the border with Turkey In pictures: Syria conflict Syria crisis Residents queue as they wait to receive food aid distributed by the UNRWA at the Palestinian refugee camp of Yarmouk, south of Damascus In pictures: Syria conflict Syria crisis Belongings of Syrian rebels inside a chapel at Crac des Chevaliers, the world's best preserved medieval Crusader castle in Syria. The village was destroyed in fighting between the government and rebel forces while the castle, listed as a UNESCO world heritage site, also has been damaged over the past two years In pictures: Syria conflict Syria crisis Hosen Sabah, a 16-year-old student is comforted by his mother at a hospital in Damascus. Nosen was wounded by a mortar outside his school, while 14 other students were killed and over 80 wounded In pictures: Syria conflict Syria crisis A Free Syrian Army fighter works on a locally made launcher before firing it towards forces loyal to Syria's President Bashar Al-Assad in Mork town In pictures: Syria conflict Syria crisis Syrian policemen and citizens inspecting the site of a car bomb at the entrance of Moadhamiyet al-Sham neighborhood in rural Damascus. According to Syria's Arab News Agency (SANA), a car bomb explosion has gone off in the countryside of Damascus and initial information say there are casualties, where a car rigged with explosions was remotely detonated at the entrance of Moadhamiyet al-Sham neighborhood in rural Damascus during engineering units it was trying to dismantled it In pictures: Syria conflict Syria crisis Opposition fighters carrying a rocket launcher during clashes against government forces in the Sheikh Lutfi area, west of the airport in the northern Syrian city of Aleppo In pictures: Syria conflict Syria crisis A Syrian man helps a woman to make her way through debris following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo In pictures: Syria conflict Syria crisis A Syrian man reacts as he carries the body of injured boy following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo. According to the Syrian Observatory for Human Rights, at least 33 civilians were killed in the attack In pictures: Syria conflict Syria crisis Syrian rescue workers carry the body of a woman following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo In pictures: Syria conflict Syria crisis A Syrian woman walks past the burning wreckage of a car following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo In pictures: Syria conflict Syria crisis A man and two children run to a safer place following reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo In pictures: Syria conflict Syria crisis A man holds an injured child after, according to activists, two barrel bombs were thrown by forces loyal to Syria's president Bashar Al-Assad in Hullok neighbourhood of Aleppo In pictures: Syria conflict Syria crisis An injured man talks on a walkie-talkie after, according to activists, two barrel bombs were thrown by forces loyal to Syria's president Bashar Al-Assad in Hellok neighbourhood of Aleppo In pictures: Syria conflict Syria crisis A man walks inside a mosque damaged by, according to activists, a barrel bomb thrown by forces loyal to Syria's president Bashar Al-Assad in Old Aleppo In pictures: Syria conflict Syria crisis Syrians gather at the site of reported air strikes by government forces in the Halak neighbourhood in northeastern Aleppo In pictures: Syria conflict Syria crisis Rebel fighters carry their weapons as they run to avoid snipers loyal to Syria's President Bashar al-Assad in the town of Morek in Hama province

The Observatory classified attacks in Khan Sheikhoun, Jasim and Doma as “massacres” and recorded deadly strikes in the provinces of Aleppo, Idlib, Hama, Daraa, Rif Dimashq and Deir Ezzor.

Among the 57 civilians killed in Monday’s raids were five children, the Observatory said, and more than 100 others were wounded.

At least 100 fighters, the presumed target of the regime's attacks, were killed in the same strikes, including rebels, Islamists and foreign militants on both sides of the conflict.

Destruction is seen following a reported barrel-bomb attack by Syrian government forces in the northern city of Aleppo (Getty Images)

The Observatory counted more than 2,000 air strikes by regime forces across Syria in January, killing 271 civilians, including 50 children and dozens of women, and injuring at least 1,000.

The cost of the damage to homes, businesses and the infrastructure could not be calculated and it is estimated that tens of thousands of people continue to be displaced.

Many strikes used barrel bombs, the group claimed. The banned weapons, favoured because of the their cheapness and blast radius, are usually oil drums or gas cylinders packed with explosives and scrap metal that are dropped from helicopters or planes.

A specialist UN Security Council resolution was passed last year to ban their use but monitors have collected evidence from multiple blast sites that they say proves barrel bombs are still raining on civilian areas.

A chemical attack killed at least 213 people in Damascus in August 2013

The Syrian Observatory for Human Rights is calling on the Security Council to issue another resolution condemning al-Assad’s regime for its “indiscriminate bombing” and to order all parties in Syria to stop using barrels bombs or heavy weapons in civilian areas.

A spokesperson called for member countries to “work harder in order to stop the war crimes and crimes against humanity committed daily against the Syrian people, and to refer the file of these crimes to international Criminal Court”.

If China and Russia continue to use their veto to prevent this, special courts should be established to deal with the Syrian regime, the Observatory recommended.

David Cameron addressing the House of Commons during the failed vote for intervention in Syria in 2013 (Reuters)

Syria's civil war so far killed more than 203,000 people, including 65,000 civilians and 10,400 children in less than four years, according to the latest estimates.

In its annual world report, Human Rights Watch accused President Assad’s forces and pro-government militias of intensifying attacks on civilian areas as well as illegally arresting, detaining, torturing and forcing the disappearance of opponents.

The international condemnation of the chemical attack on Ghouta in 2013 had not been followed up with justice for victims, the organisation said, and although the subsequent Chemical Weapons Convention saw Syria agree to destroy all declared chemical arms, chlorine gas continues to be used.

People stand near damaged buildings along a street at a site hit by what activists said was a barrel bomb dropped by forces loyal to Syria's President Bashar al-Assad in Aleppo (Reuters)

Human Rights Watch documented the use of other illegal weapons, including cluster bombs.

“The extremist group Islamic State and al-Qaeda’s affiliate in Syria, Jabhat al-Nusra, were responsible for systematic and widespread violations including targeting civilians, kidnappings, and executions,” the report noted.