Gunmen opened fire on vehicles carrying Shiite Muslims in Pakistan’s restive northwest on Thursday, killing at least 42 people, including six women, and wounding 20 others in one of the region’s deadliest such attacks in recent years, police said, AP reports.

At least 10 passengers were in critical condition at a hospital, Local police said.

The attack happened in Kurram, a district in Khyber Pakhtunkhwa province where sectarian clashes between majority Sunni Muslims and minority Shiites have killed dozens of people in recent months.

No one immediately claimed responsibility for the latest attack. It came a week after authorities reopened a key highway in the region that had been closed for weeks following deadly clashes.