Syria's armed forces on Monday announced the extension of a nationwide ceasefire for an additional 72 hours, despite ongoing fighting in Aleppo, the country's economic powerhouse before the conflict.

"A regime of calm will be extended for a period of 72 hours from one o'clock (local time) on July 12," the armed forces said in a statement.

The extension marks the second of its kind since Damascus announced the initial "cessation of hostilities" on Wednesday in respect of the Eid al-Fitr celebration, which marks the end of Ramadan. However, heavy fighting continued in Aleppo and other parts of Syria.

The UK-based Syrian Observatory for Human Rights (SOHR) reported that rebel groups on Monday fired at least 300 shells into government positions in the city, days after the Syrian army cut off a main supply route.

"All kinds of heavy artillery and machine-guns are being used in the assault, which is intended to ease the pressure" on other fronts, said Mahmoud Abu Malak, spokesman for the Nureddin al-Zanko rebel group.

Meanwhile, government air raids on rebel-held parts of Aleppo killed at least 13 civilians near the front line, SOHR said.

"The opposition has not advanced because of the heavy aerial bombardment the regime is carrying out on the areas where fighting is underway," said SOHR chief Rami Abdel Rahman.

How the Syrian civil war began - and gave 'Islamic State' room to grow The "Arab Spring" effect In 2011, as regimes crumble across the region, tens of thousands of Syrians take to the streets to protest against corruption, high unemployment and soaring food prices. The Syrian government responds with live ammunition, claiming some 400 lives by May.

How the Syrian civil war began - and gave 'Islamic State' room to grow Condemnation without consensus At the urging of Western countries, the UN Security Council condemns the violent crackdown. The EU and US implement an arms embargo, visa bans and asset freezes in the months that follow. With the backing of the Arab League, calls eventually grow for the Syrian president's departure. But not all UN members agree with this demand.

How the Syrian civil war began - and gave 'Islamic State' room to grow Assad refuses to back down Bashar al-Assad - who has been in power since the death of his father in 2000 - sees his reputation wane with the continuing unrest. He refuses to end decades-long emergency rule, which allows for surveillance and interrogation. Russia backs its ally, supplying weapons and vetoing UN resolutions on Syria multiple times.

How the Syrian civil war began - and gave 'Islamic State' room to grow The opposition gets organized By the end of the year, human rights groups and the UN have evidence of human rights abuses. Civilians and military deserters are slowly beginning to organize themselves to fight back against government forces, which have been targeting dissidents. More than 5,000 have died so far in the fighting. It will take another six months before the UN acknowledges that a war is taking place on Syrian soil.

How the Syrian civil war began - and gave 'Islamic State' room to grow Outside intervention In September 2012, Iran confirms that it has fighters on the ground in Syria - a fact long denied by Damascus. The presence of allied troops underscores the hesitance of the US and other Western powers to intervene in the conflict. The US, stung by failed interventions in Afghanistan and Iraq, sees dialogue as the only reasonable solution.

How the Syrian civil war began - and gave 'Islamic State' room to grow Fleeing the conflict As the death toll nears 100,000, the number of refugees in neighboring countries - such as Turkey and Jordan - hits one million. That number will double by September 2013. The West and the Arab League have seen all attempts at a transitional government fail in the two years of war, watching as fighting spills over into Turkey and Lebanon. They fear Assad will stay in power by any means possible.

How the Syrian civil war began - and gave 'Islamic State' room to grow No united front against Assad Assad has long claimed he's combatting terrorists. But it's not until the second year of war that the fragmented Free Syrian Army is definitely known to include radical extremists. The group Al-Nusra Front pledges allegiance to al Qaeda, further splintering the opposition.

How the Syrian civil war began - and gave 'Islamic State' room to grow From brute force to chemical warfare In June 2013, the White House says it has evidence that Assad has been using sarin nerve gas on civilians - a report later backed by the UN. The discovery pushes US President Barack Obama and other Western leaders toward considering the use of military force. However, Russia's proposal to remove the chemical weapons ultimately wins out.

How the Syrian civil war began - and gave 'Islamic State' room to grow Islamic State emerges Reports of a new jihadist group calling itself the Islamic State of Iraq and the Levant (ISIL) emerge in the final weeks of 2013. Taking land in northern Syria and Iraq, the group sparks infighting among the opposition, with some 500 dead by early 2014. The unexpected emergence of IS ultimately draws the US, France, Saudi Arabia and other nations into the war. Author: Kathleen Schuster



'Push the peace process'

More than 280,000 people have been killed and millions more displaced since the conflict erupted in 2011, when government forces launched a violent crackdown on peaceful protesters calling on President Bashar al-Assad to step down.

Peace talks have effectively broken down between Damascus and the Saudi-backed High Negotiations Committee (HNC), the main opposition alliance in Syria, since a US-Russia brokered "cessation of hostilities" collapsed.

"There is a need to adopt a new strategy to push the peace process by adopting a tougher policy against the regime's violations against the Syrian people … before calling for a new round of negotiations," the HNC said in a statement.

Meanwhile, UN Syria envoy Staffan de Mistura said all parties should continue working towards a political solution to end the five-year conflict.

"More than ever, the key is a possible deal between Russia and America, because they are the ones who … pulled off the miracle of the two-month truce," said de Mistura.

US State Secretary John Kerry is expected to visit Moscow this week to discuss the conflict with Russian officials.

Watch video 03:03 Aleppo: 'Stop the bombs' | @dwnews

ls/kl (Reuters, AFP, AP)