Militants stepped up attacks across Iraq yesterday, killing at least 30 people in a spate of bombings and shootings that followed a threat by al Qaeda to launch a new phase of violence.

The US military announced it had caught a suspected al Qaeda militant believed to be responsible for the killing last week of a key Sunni Arab tribal leader in Anbar province.

Sheikh Abdul Sattar Abu Risha, who met US President George W. Bush two weeks ago in Anbar, was killed in a bomb attack on Thursday near his home. He led an alliance of tribes that helped US troops push al Qaeda out of much of the vast western area.

Suspected al Qaeda militants shot dead 14 people in the predominantly Sunni Arab town of Muqdadiya north of Baghdad and torched at least 12 shops in the town, Iraqi police said. A suicide bomber also killed six people at an outdoor cafe in the northern town of Tuz Khurmato. In Baghdad, eight people were killed in four separate bombings.