Six Pakistani soldiers were killed on Tuesday in a clash with Islamist militants in a northwestern region near the border with Afghanistan, the army said, adding that four of the militants were killed.

The Pakistani Taliban claimed responsibility saying its fighters had ambushed two military vehicles.

"During an intense exchange of fire, six brave soldiers, having fought gallantly, embraced martyrdom," the army said in a statement, adding that the clash took place in North Waziristan.

The rugged border region has long served as a safe haven for militants linked both to domestic Islamists who have been fighting against the state and the Afghan Taliban, before they returned to power in Kabul in 2021.

The Pakistani Taliban, known as the Tehreek-e-Taliban Pakistan (TTP), said in a statement its fighters had killed 18 soldiers in the ambush.

Reuters was not able to verify the battlefield accounts. The army keeps the area off limits to journalists and human rights activists.

The TTP is an umbrella organisation of several Sunni Muslim Islamist and sectarian groups trying to overthrow the government. The TTP has stepped up its attacks since it scrapped a ceasefire with the government last year.

Reporting by Asif Shahzad; Additional Reporting by Saud Mehsud in Dera Ismail Khan; Editing by Alison Williams and Clarence Fernandez