An air strike on a camp for internally displaced Syrians near the country's border with Turkey has killed at least 30 people, activists said.

The attack on the camp in Idlib province on Thursday also left dozens of others injured. A number of those killed were children, according to the UK-based Syrian Observatory for Human Rights.

The Observatory said the dead included women and children and the death toll from the air strikes was likely to rise.

However, the Syrian military said on Friday that it did not target the camp, state news agency SANA reported.

Russia's military also insisted that none of its aircraft flew over the refugee camp the, suggesting on Friday that Al-Qaeda-linked Al-Nusra Front could have shelled the location.

"We have attentively studied the information from the air space monitoring data in this area for May 4 and 5, 2016. There were no flights by Russian or any other aircraft," spokesman Igor Konashenkov told Russian news agencies.

"Judging by the damage shown in photographs and video, the camp may have been shelled either on purpose or by mistake by multiple rocket launchers which are currently being used very actively in this area by terrorists from Al-Nusra," Konashenkov said.

However, Al Jazeera's Zeina Khodr, reporting from the Turkish city of Gaziantep, said activists were split on whether Russian or Syrian planes were behind the attack.

"Many in the opposition believe that with strikes like this there's proof the government is not serious about the cessation of hostilities," Khodr said.

"These people [internally displaced] live close to the Turkish border in search of safety...they think that the closer they are to the border, the safer they are."

Video of the incident posted on social media showed tents on fire and victims buried underneath debris as rescuers tried to put out flames.

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Under-Secretary-General for Humanitarian Affairs, Stephen O'Brien, called for an immediate, impartial and independent investigation into the air strikes, which, if found to be deliberate, could amount to a war crime.

"All parties to this appalling conflict should understand that they will one day be held accountable for violations of international humanitarian and human rights law."

He said that initial reports indicate that at least 30 people were killed, and more than 80 injured, among them many women and children, while dozens of tents were destroyed or badly damaged.

Idlib is not part of the partial ceasefire that was announced yesterday after an agreement between the US and Russia.

Aleppo bombardment

The attack is the latest deadly strike on civilians in Syria, with much of the recent focus on the divided city of Aleppo where nearly 300 people were killed in nearly two weeks of air strikes and shelling.

Syrian rebels seized on Friday Khan Touman, a village from government forces near Aleppo overnight, the Observatory reported, gaining important ground near the Syrian city where the US and Russia are trying to de-escalate the war.

The Observatory said that at least 73 people were killed in the battle which took place some 15km southwest of Aleppo in a location near the Damascus-Aleppo highway.

While multiple rebel sources said it had been captured, a Syrian army source denied Khan Touman had been taken.

The attack was launched by an alliance of armed groups known as Jaish al-Fatah, including al-Nusra Front, which has rejected diplomatic efforts to halt the war and promote peace talks.

The US and Russia this week brokered a ceasefire in the city of Aleppo itself.

"Throughout the night the battles were very intense," said Abu al-Baraa al-Hamawi, a fighter from the Ajnad al-Sham group, one of the factions taking part in the attack. "Areas south of Khan Touman have been liberated," he told Reuters news agency.

The Observatory said 43 of the dead were rebels and 30 were government forces.

Groups fighting under the banner of the Free Syrian Army, which have mostly supported diplomatic efforts in Syria, were not taking part in the attack, a fighter from one Aleppo-based FSA group told Reuters.

Syria's government has been at war with rebels after it violently put down an initially peaceful uprising against President Bashar al-Assad five years ago.

An estimated 400,000 people have been killed in the conflict, according to the UN, with millions more displaced internally and in neighbouring states.

The crisis has also given rise to the European refugee crisis, as Syrians join hundreds of thousands of others in seeking refuge on the continent.