DAMASCUS: Dozens of people have been killed in separate attacks in Syria's north, marring what is supposed to be a festive holiday in the country and worldwide.

Syrian army planes on Friday, the first day of Eid Al-Fitr, dropped barrel bombs on the town of Al-Bab in Aleppo province, killing at least five people and injuring 11 other, activists have said.

The attack on the town, which is under control of Daesh, comes a day after a bombardment campaign by President Bashar Assad’s forces that left 11 people dead. In Idlib province, just after the end of Ramadan was announced on Thursday evening, 17 people died in a barrel bombardment on the village of Maarat Masrin. Another 11 people were killed in the village of Ourm Al-Joz.

Away from the violence, the Syrian news agency SANA published photographs showing a smiling Assad surrounded by religious figures as they performed Eid prayer at a mosque in the capital Damascus.

SANA reported that he was accompanied by "high-ranking officials from the (ruling Baath) party and from the state”.

The agency said the mosque's imam, Sheikh Mohammad Sharif Al-Sawaf, "prayed to God to save Syria, its leader, its army and its people, and to bring victory against its enemies".

Meanwhile, British pilots have taken part in US and Canadian airstrikes against Daesh in Syria, the Defense Ministry said on Friday, despite Parliament voting in 2013 against military action.

Prime Minister David Cameron knew British military pilots were taking part in the bombing raids, his spokeswoman said. Some lawmakers have called for ministers to explain the situation in Parliament.

"The UK is not conducting airstrikes in Syria," the ministry said.

"But we have a long-standing embed program with allies, where small numbers of UK personnel act under the command of host nations.

"That has been the case in Syria, although there are currently no pilots operating in this region," it said, adding that the number of pilots involved was fewer than 10.