Turkish special soldiers crossed the Iraqi frontier Tuesday as part of a "hot pursuit" of PKK rebels who were involved in a roadside bomb attack that killed 16 soldiers on Sunday, according to an unnamed Turkish government official.

"This is a short-term measure intended to prevent the terrorists' escape," the official said on condition of anonymity.

Turkish media, citing unnamed military sources, said two battalions from Turkey's special forces had crossed the border.

Meanwhile, attacks on Turkish security forces continue to escalate.

The bombing of a minibus ferrying Turkish police to a border gate in the Igdir province killed at least 14. Hours later, three Turkish police officers were killed in a rocket-propelled grenade attack by Kurdistan Workers Party (PKK) militants on their armored vehicle, a security source told the Reuters news agency.

The second attack in the southeastern city of Cizre brings Tuesday's death toll of Turkish forces to at least 18.

Turkey's state-run Anadolu news agency said Turkish jets had carried out airstrikes against a group of Kurdish rebels as well as the militants' camps in northern Iraq. It said up to 40 rebels died in the overnight aerial operations.

The airstrikes were confirmed by Firat news, a website close to the outlawed PKK.

Anadolu said F-16 and F-4 fighter jets struck a group of up to 25 PKK rebels believed to have carried out the bombing with improvised explosive devices that killed the 16 soldiers near the border with Iraq on Sunday.

The report said 53 planes were involved in the strikes.

Protests denouncing the PKK erupted in several cities across Turkey on Monday soon after the military announced the death of the 16 soldiers.

The pro-Kurdish Peoples' Democratic Party (HDP) said more than two dozen of its local branches were vandalized during the demonstrations even as its leaders have appealed for a return to the ceasefire which until July had held since 2013.

Spiraling violence

More than 200 people have been killed in the renewed fighting between the PKK and the security forces since July, including close to 100 soldiers and police officers.

It comes amid increased political uncertainty in Turkey. The country is holding another election on November 1 following the ruling party's failure to form a coalition government following the June polls.

The PKK has also released 20 Turkish citizens, including customs officials, kidnapped last month by the militants in the east of Turkey and shuttled to Iraq.

The guerilla group handed the 20 over to a delegation consisting of human rights activists, Iraqi Kurdistan officials and members of the HDP who had travelled to Iraq, security sources in eastern Turkey told the AFP news agency

The customs officials are expected to cross back into Turkey late Tuesday, the official said.

jar/cmk (AP, AFP, Reuters, dpa)