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.

An al Qaeda-led group, the Islamic State in Iraq, said on Saturday it was launching a fresh round of attacks to mark the Muslim holy month of Ramadan, which started late last week.

A sustained campaign of violence would undermine US and Iraqi assertions that a seven-month security crackdown had disrupted the Sunni Islamist network?s operations in and around the Iraqi capital while also reducing attacks from other groups.

Bush, announcing a limited withdrawal of around 20,000 US troops by July, last week said the cuts were possible because US forces had made significant progress in improving security and ?ordinary life is beginning to return? to Baghdad.

The Islamic State in Iraq, believed to be a front for the main al Qaeda in Iraq network, has said it was behind the killing of Abu Risha. It has warned it would target other tribal leaders who cooperated with security forces.

The US military named the captured militant believed to be behind Abu Risha?s killing as Fallah al-Jumayli. ?Intelligence reports indicate al-Jumayli is involved in a plot to kill key leaders in the tribal awakening,? a US military statement said, referring to the Anbar tribal alliance.

<B>Plot to kill tribal leaders</B>

On the political front, cleric Moqtada al-Sadr?s political movement said it had no immediate plan to bring down Prime Minister Nuri al-Maliki?s government despite pulling out of his ruling Shi?ite Alliance.

Sadr?s bloc withdrew from Maliki?s parliamentary coalition on Saturday, leaving him with the support of only about a half of the legislature?s 275 lawmakers.

?We have many reservations about Maliki?s government but we haven?t discussed a vote of no confidence yet because it?s still too early to talk about this matter,? said Salah al-Ubaidi, a spokesman for the Sadr movement.

Maliki can still count on the backing of two Shi?ite Islamist parties and the two main Kurdish parties in parliament, and could probably survive with the support of a handful of independent lawmakers.

Police said seven people were wounded in the shootings in Muqdadiya, which lies in Diyala province where al Qaeda in Iraq militants have had a strong presence until recent US and Iraqi offensives.

The motive for the attack was unclear, but some Sunni Arab tribes in Diyala have begun to follow Abu Risha?s example of cooperating with US and Iraqi security forces.

In other violence yesterday, two members of local municipal councils in Baghdad were killed, officials said.