At least 29 people, all believed to be rebels, were killed and around 20 others wounded in an explosion near Syria's border with Turkey on Thursday, Al Jazeera reported. The Islamic State group claimed responsibility for the attack.

The Syrian Observatory for Human Rights, a British monitoring group, said the blast took place during change of guard at the rebel-controlled Atmeh crossing. Officials are verifying whether the explosion was triggered by a suicide bomber or a device. Syria-based Local Coordination Committees said the blast was triggered by a explosives-laden bag planted near the border.

The fatalities included the head of the top civil judicial body in rebel-held eastern Aleppo, Sheikh Khaled al-Sayyed, and a judge who worked with him, according to Reuters. A witness said that a majority of the deceased were associated with the Failaq al-Sham group, which has been collaborating with Turkish-backed factions known as the "Euphrates Shield". The Turkish government told BBC that it will continue its offensive, with the aim to create a de facto buffer zone close to its vulnerable border.

The Islamic State group considers Atmeh a priority location because Islamic prophecies say it is the site of an end-of-times battle between Muslims and their "Roman rivals" – a term the extremist group has now expanded to include the Unite States and its allies, BBC reported.

In August, at least 32 rebels were killed in an Islamic State group-planned blast at the Atmeh crossing. Rebels use the point to travel from Syria's Idlib via Turkey to challenge the terror outfit. More than three lakh people have died in the six-year-long civil war in Syria, and nearly half the country's population was forced to flee since it began. While the US supports rebel groups, Russia is seen as a key ally of Syrian President Bashar al-Assad.