BASRA, Iraq – Iraq’s new prime minister declared a state of emergency yesterday in the southern city of Basra, vowing to crack down with an “iron fist” on rival gangs battling each other for power.

A car bomb in the northern city of Mosul, meanwhile, killed five policemen, the latest insurgent attack during an especially bloody week.

Violence has been escalating in Shiite-dominated Basra, with a wave of kidnappings and the slayings of nearly 140 people – mostly Sunnis but also Shiites and police – in May alone, police said. The tension has been brewing largely due to the growing influence of an anti-American cleric, Muqtada al-Sadr, and his Mahdi Army, and the armed Badr organization, both Shiite groups.

Prime Minister al-Maliki, himself a Shiite, declared the month-long state of emergency during a visit to the oil-rich region, a top Shiite official traveling with him, Syed Muhammad al-Haidari, said. Mr. al-Maliki gave a strong denunciation of the violence that Sunni religious leaders have blamed on Shiite death squads.

“We shall use an iron fist against the leaders of the gangs or those who threaten security,” he said earlier in a speech, apparently referring to the militias as well as rival tribal groups. “And we shall ask all security departments to draw up an effective and quick plan to achieve security.

“The size of the security power in this province as far as I know should be sufficient to maintain full control of the security situation, but it seems that these forces are useless with the deteriorating of the security situation in this town,” he told about 700 tribal sheiks, religious leaders, officials, army officers, and other residents.

It is the only state of emergency in effect, Interior Ministry Undersecretary Major-General Ahmed Al-Khafaji said from Basra. Other cities, including Baghdad and Ramadi, have curfews.

Mr. al-Maliki said his trip to Basra was an effort to “heal the rift and find a solution for what caused the latest events.”

Britain has about 8,000 troops in the area, along with those of other countries. In the months after the 2003 invasion, British troops enjoyed relative peace in the south, compared with the restive Sunni regions farther north.

But now violence has escalated. Two British soldiers were killed in a roadside bombing Sunday in Basra, bringing to nine the number of British personnel who have died in the city this month and pushing total British deaths since 2003 to 113. American deaths, meanwhile, are approaching 2,500.

Shiite anger also has been stoked by a perceived shift in American policy since the arrival of American Ambassador Zalmay Khalilzad, a Sunni Muslim who has criticized the Shiite-led Interior Ministry for human rights abuses and made overtures to Sunni insurgents in hopes of getting them to disarm.