Government officials met with tribal leaders in northwestern Pakistan on Sunday to try to mediate a ceasefire between rival sectarian groups after days of clashes that have killed at least 68 people and injured dozens.

The clashes started after gunmen attacked convoys of civilian vehicles on Thursday, killing at least 40, mostly Shi’ite Muslims. That sparked retaliatory attacks against Sunni residents and there have been pitched battles between armed groups from both sides.

Armed Shi’ite…