A massive bomb explosion has ripped through a military vehicle in Turkey’s Kurdish-dominated southeastern region, killing at least four soldiers and injuring nine others, security sources say.

The military said on Wednesday that the bomb was detonated as the vehicle was traveling in the town of Semdinli in the Hakkari Province near the Iraqi border. 

Explosives had been laid in the road in advance of the soldiers’ convoy.

The Turkish military has reportedly deployed troops backed by helicopters to the troubled region to launch an operation in the wake of the fatal attack.

Earlier on Wednesday, a Turkish soldier was killed when he came under militant fire in the mainly Kurdish town of Nusaybin, situated at the Syrian border. The volatile town has been under a round-the-clock curfew for more than two months as Turkish forces attempt to root out militants.

Turkish fighter jets also bombarded overnight areas in Hakkari Province and in northern Iraq, killing at least 10 people.

he Turkish military has launched a large-scale military campaign against PKK militants in its southern border region since last year. The government has imposed curfew in the areas that have been targeted in the army’s anti-PKK campaign.

The Turkish military has also been pounding the group’s positions in northern Iraq.

The operations began in the wake of a deadly July 2015 bombing in the southern Turkish town of Suruc. More than 30 people died in the attack, which the Turkish government blamed on the Daesh Takfiri terrorist group.

After the bombing, the PKK militants, who accuse the government in Ankara of supporting Daesh, engaged in a series of reprisal attacks against Turkish police and security forces, prompting the Turkish military operations.

A shaky ceasefire between Ankara and the PKK that had stood since 2013 was declared null and void by the militants following the Turkish strikes against the group.

The PKK has been fighting for an autonomous Kurdish region in southeastern Turkey since 1984. The conflict has left thousands of people dead.