Iraq's new Prime Minister declared a state of emergency today in the southern city of Basra, where British troops have been dragged into a bloody power battle between sectarian militias.

Nouri al-Maliki, who took office last week at the head of a grand coalition of Shia and Sunni Muslims and Kurds, announced the 30-day emergency period on a visit to the oil-rich city, where hundreds have been killed in recent weeks by Shia militias.

A state of emergency also has been imposed on Baghdad, and the provinces of Diyala, on the Iranian border, and Anbar, which has a huge land border with Syria, Jordan and Saudi Arabia.

Details are unclear but an Iraqi security source said that it would involve day-and-night patrols by security forces and increased vehicle searches.

Britain has some 8,000 troops in the southern province who have increasingly become the target of militia attacks. In the the bloodiest month for UK forces since the invasion of Iraq three months ago, nine British service personnel have been killed so far in May.

Mr Standing at a podium with an Iraqi flag as a backdrop, Al-Maliki issued a strong denunciation of a wave of killings and kidnappings in Basra that Sunni religious leaders have blamed on Shia death squads.

"We shall use an iron fist against the leaders of the gangs or those who threaten security," he said, apparently referring to the militias as well as rival tribal groups.

"We shall ask all security departments to draw up an effective and quick plan to achieve security."

Mr Al-Maliki was addressing about 700 tribal sheikhs, religious leaders, officials, army officers and other residents in Iraq’s second-largest city, which lies 340 miles southeast of Baghdad.

Shouting broke out in the auditorium before Mr al-Maliki delivered his speech, with several tribal leaders accusing local officials and security forces of being behind the mounting violence. But the Prime Minister calmed them down from the podium, saying: "We cannot negotiate with everybody shouting."

Mr al-Maliki, a Shia Muslim, travelled to Basra with his Sunni Arab Vice-President, Tareq al-Hashemi. Both men said that security must be restored before prosperity could be restored to the strategic port city.

"There are future plans to improve Basra," Mr al-Hashemi said. "But to prepare suitable circumstances, security must be restored and that is why we are here."

Iran’s hand is rumoured to be behind Shia militias in Basra, although little evidence of a direct link has been made public. Nevertheless, US officials have long accused the Iranians - though not necessarily the Tehran government - of smuggling weapons to Shia militias in Basra and perhaps also selling roadside bomb technology to Sunni militants - charges Iran denies.

"Basra is no exception from what is taking place in Baghdad, Anbar, Nineveh and Diyala," Mr al-Hashemi said, referring to other volatile provinces. "There are malignant campaigns and malignant intentions and there are malignant agendas to deepen divisions among Iraqis. They intend to divide the country."

In the months after the 2003 invasion, British troops enjoyed relative peace in southern Iraq compared with the restive Sunni regions further north. But violence in the region has escalated. Nearly 140 people, most Sunnis but also Shias and policemen, were killed in Basra this month alone, a senior police official said.

Lieutenant-General Sir Rob Fry, who as deputy commander of all multinational forces in Iraq is the most senior British officer in the country, told The Times earlier this month that British troops could be sent in to take on the extremist militias in Basra if the Iraqi army fails to do the job.

Violence continued elsewhere in Iraq, a day after car bombs targeting Shia areas destroyed a car dealership in southern Iraq and a bustling outdoor market north of Baghdad. Altogether 54 people and 120 were wounded in yesterday's violence.

Today a parked car packed with explosives hit a police patrol in the northern Iraqi city of Mosul, killing at least five policemen and wounding 14, including a senior officer. Jamal Kadhim Hassoun al-Zamili, former governor of Diwaniyah city south of Baghdad, was killed in a drive-by shooting last night that also wounded two of his guards.

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