The interior minister faced calls for his dismissal because of the worsening security crisis in Baghdad and surrounding towns, mostly blamed on sectarian conflict between Shias and Sunnis.

Gunmen in military fatigues drove to the main shopping area of Karrada in 15 vehicles and split into two groups, one going into a mobile phone shop and the other into the office next door of the Iraqi-American Chamber of Commerce, said police Lt. Thair Mahmoud.

They kidnapped 15 staff and customers from the shop and 11 from the chamber, he said. All were believed to be Iraqis. No other details were available.

In a second kidnapping, gunmen in commando uniforms, blocked a car carrying a millionaire businessman and his two sons, seizing the three in southeastern Baghdad, said police Lt. Bilal Ali Majeed.

Kidnappings for ransom have become rampant in recent months. Abductions are believed to be a major source of income not only for criminal gangs but also insurgents fighting US and Iraqi forces.

The suicide bomber detonated a pickup truck near an Iraqi observation post outside the northern city of Mosul, killing four soldiers and wounding six, said an army officer who spoke on condition of anonymity because he was not authorized to release such information.

A day earlier, gunmen ordered four policemen and a lawyer out of their car and beheaded them near the northern town of Hawija, 150 miles north of Baghdad, said police Col. Burhan Tayeb.

Several key Iraqi parliament members are pressing to replace Interior Minister Jawad al-Bolani, who is responsible for police and paramilitary commandos, at the forefront of the fight against extremists in the capital.

Al-Bolani, a Shia, was chosen for the sensitive post after protracted negotiations among the various religious and ethnic parties within the national unity government. The interior and defence posts were filled in June, nearly three weeks after the rest of the Cabinet.

Earlier four US marines were killed in combat in Iraq's restive western province of Anbar, the US military reported on Sunday.

The marines, part of Regimental Combat Team 7, died on Saturday, just two days after four more marines were killed in two incidents in the same province.