This photo shows a missile fired by the militant group against Syrian government forces position in Idlib on Tuesday.

Syrian insurgents launched counterattacks Tuesday in and near areas recently taken by government forces in the country's last remaining rebel region, after a series of setbacks they suffered in recent weeks, opposition activists said.

The fierce fighting killed more than 50 fighters on both sides, according to the Britain-based Syrian Observatory for Human Rights. It also underscored that President Bashar Assad's forces will face a long, hard fight as they try to chip away at the last rebel-held territory.

The counterattacks began early in the morning and government forces called in Syria's air force to repel them, the Observatory said. It said 29 Syrian troops and pro-government gunmen were killed, as well as 23 insurgents.

The insurgents captured two villages, Salloumieh and Abu Omar, and pushed into the nearby village of Sham Al Hawa, it said.

The Ibaa media outlet of the Al Qaeda-linked Hayat Tahrir Al Sham militant group said its fighters were attacking Syrian positions east of Khan Sheikhoun, a major town that was held by rebels until they lost it last week.

Pro-government activists said on social media that Syrian troops and pro-government gunmen are repelling the attack.

Syrian government forces captured wide areas from insurgents over the past weeks in an offensive that began on April 30. The areas taken include all rebel-held parts of Hama province as well as villages on the southern edge of Idlib, the last remaining rebel stronghold in Syria.

Tuesday's clashes came after Syrian warplanes pounded the rebel-held town of Maaret al Numan and nearby villages over the past two days - their likely next target for takeover.

Maaret Al Numan, like Khan Sheikhoun, sits on the highway linking Damascus with the northern city of Aleppo, Syria's largest. Government forces are trying to eventually open that highway.

Taher Al Omar, a citizen journalist with the Al Qaeda-linked militants, wrote on social media that they have carried out several suicide attacks so far.

The months of fighting have displaced more than half a million civilians toward northern parts of Idlib, already home to some 3 million people, according to UN humanitarian officials.

Elsewhere in northern Syria, a bomb exploded on a minibus, killing two people and wounding nine near the town of Azaz. The town is controlled by Turkish troops and Turkey-backed opposition fighters, according to pro-government media and the Azaz media center, an activist collective.

Associated Press