Air strikes have killed at least 22 people in Syria's northwestern Idlib province, as a government-announced ceasfire entered its third and final day and pro-government forces continued a push to encircle rebel-held areas of Aleppo city. 

Dozens of others were injured after air strikes hit the town of Darkush, near the Turkish border in western Idib, according to the Britain-based Syrian Observatory for Human Rights. 

"The toll of the attack is now 22 people, including a child and seven women," observatory chief Rami Abdel Rahman said on Friday afternoon 

Darkush is held by the al-Qaeda affiliated al-Nusra Front and allied rebel groups, which control the entirety of northwestern province of Idlib. 

A Facebook page run by activists in the town posted photographs showing a column of grey smoke curling out of a town tucked in verdant hills.

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It said some of the wounded had been transferred to nearby hospitals, and others across the border inside Turkey.

The UK-based observatory had no immediate word on who carried out the strikes but said that it was likely to have been either the Syrian government or its ally Russia, rather than the US-led coalition.

Syria war: Fighting blocks only road to Aleppo

The Syrian army announced on Wednesday that it would observe a 72-hour nationwide ceasefire for Eid al-Fitr, the feast marking the end of the Islamic holy month of Ramadan.

But on Thursday, pro-government forces made major steps towards completely encircling the rebel-held parts of Aleppo, capturing high ground overlooking the strategic Castello Road - the only road into and out of the opposition half of the city. 

“The Syrian government is now closer than ever to achieving its goal of surrounding Aleppo. This would isolate the city from other opposition controlled areas and from the border with Turkey. For the opposition, it’s a fight for survival," Al Jazeera's Zeina Khodr said on Friday, reporting from the Syria-Turkey border.

“It’s also a question of survival for the estimated 300,000 people living in the eastern districts of Aleppo. A siege would only cause more suffering in a city devastated by years of war. “

Nearly 600,000 Syrians are living under siege in 18 communities across the country, according to figures from the United Nations. If Aleppo is surrounded by government forces, it will become number 19.

“The people are afraid of a siege. The road is totally closed right now. We may have enough goods and medicine for a month," Aleppo-based media activist Mujahid Abu Joud told Al Jazeera.

"If the government succeeds, it will be the first time the city is besieged.”

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The Kremlin said on Wednesday that President Vladimir Putin and his US counterpart Barack Obama had agreed to "intensify" military coordination in Syria.

The White House said that the two leaders had "confirmed their commitment to defeating ISIL and the al-Nusra Front".

Last month, air strikes on the provincial capital Idlib city killed at least 21 civilians, including five children.

Russia launched air strikes in support of the Damascus regime in September, one year after the international coalition, which was bombing the Islamic State of Iraq and the Levant (ISIL, also known as ISIS) group in Iraq, extended its raids to Syria.

More than 280,000 people have been killed in Syria since the country's civil war erupted in 2011, starting with peaceful protests that swiftly escalated into an armed rebellion increasingly dominated by jihadist groups.

Source: Al Jazeera and agencies