A massive explosion in Syria’s northwestern Idlib province killed more than 30 government troops on Tuesday, in an operation rebels staged to “liberate” a checkpoint on a strategic highway.

Rebels set off tons of explosives in a tunnel running beneath the checkpoint in Maarat al-Numan, just a few miles east of Talmenes, a town that was allegedly the target of chlorine gas attacks in recent weeks.

The video below, shared by a local activist, shows the huge blast, reportedly coordinated by several rebel groups.

The videos below, shared by rebel groups and activists, also show the explosion and the immediate aftermath of the blast.

Rebels talk about the successful “liberation” of the checkpoint in the footage below.

The clips below, shared by local activists, claim to show evidence of a chemical attack on Talmenes on April 21.

The first footage shows pieces of the bomb and lifeless animals that show no clear signs of injury. The next videos show victims coughing and receiving treatment for respiratory problems, reportedly as a consequence of the bombing.

Intensifying fighting in the strategic region has displaced tens of thousands of people over the last days, according to the Syrian Observatory for Human Rights, a UK-based monitoring group.

More than 150,000 people are estimated to have been killed since the beginning of the conflict in Syria.

Follow Alice Speri on Twitter: @alicesperi