Four police killed in ambush in northwestern Pakistan

Gunmen opened fire on a police vehicle and killed four officers in northwestern Pakistan on Tuesday, officials said, in a region once riven by militant violence but since cleared following military crackdowns.

The ambush in the Dera Ismail Khan district of Khyber Pakhtunkhwa was the first major attack in the area since a political candidate was killed in a suicide blast in the lead-up to Pakistan's general election in July. "The officers were out patrolling the area when six to seven people who were waiting for them opened fire on their vehicle," senior police official Mohammad Iqbal told Reuters.

"The assailants were seated at a local tea stall and opened fire when the police vehicle approached." Iqbal said four police were killed and three wounded. One senior police officer was said to be in critical condition.

No group has claimed responsibility. Dera Ismail Khan sits at the edge of Pakistan's former tribal areas that border Afghanistan, large swaths of which were once controlled by the Pakistani Taliban before military operations in 2009 and 2014 ended militant control of the region. (Writing by Saad Sayeed; Editing by Nick Macfie)