US warplanes bombed Shia militiamen in Basra last night and helicopter gunships fired rockets in militia-controlled areas of Baghdad, as Iraqi government forces proved incapable of dislodging die-hard rebels on their own.

Nouri al-Maliki, the Iraqi prime minister who has staked his reputation on crushing rogue militias, appeared to be wavering in his resolve, extending a deadline for fighters to give up and offering cash as an incentive to surrender their weapons.

British and US officials denied Iraqi news reports and statements by Basra residents that US Marine snipers had taken up positions in the southern port city, for five years under British military control. They admitted, however, that US troops were patrolling in Sadr City, the huge Shia slum in Baghdad that is controlled by the Mahdi Army militia of Hojatoleslam Moqtada al-Sadr.

The British Embassy in Baghdad said the army was ready to send in troops to back up the Iraqi army should it need combat support. “These operations are going to take time,” an embassy statement said. “Britain fully supports the government of Iraq in this important task. British coalition forces, in their overwatch role, stand ready to support Iraqi security forces operationally, as and when the government of Iraq requests this.”

Major Tom Holloway said that US warplanes twice bombed militiamen in Basra overnight. “It was on identified rocket teams in the city and there was a concentration of militia troops which was bombed,” he said.

Street-fighting had calmed slightly after three days of heavy clashes, as the government imposed a three-day total curfew in Iraq, although sporadic fighting sputtered on and militiamen were still lobbing mortars at Iraqi army positions in Basra.

The Mahdi Army was engaged in heavy fighting with police in the southwestern city of Nasariyah. The coalition has a huge logistics base outside the city that controls the convoy route from Kuwait to Baghdad, the road that provides most supplies for coalition forces in the capital.

A day after Mr al-Maliki had sworn to fight powerful Shia militias “to the end” he appeared to soften his tough stance and offered them until April 8 to surrender heavy and medium weapons. He also offered cash to those who comply, a tactic the American military used in 2004 when they failed to crush the Mahdi Army in fighting in Sadr City. The fighters handed in mostly old weapons, took the cash and rearmed for a brutal resurgence in early 2006, when full-scale sectarian warfare broke out in Baghdad.

A Mahdi Army spokesman in Sadr City said: “We are still fighting. Nobody handed in their weapons, we will never do that for cash.”

In Basra, locals said that Mahdi Army fighters were building bunkers and planting roadside bombs inside the slum areas they controlled, a sign that they were bracing themselves for a renewed government assault.

Iraqi television showed footage of Mahdi Army fighters shooting at government troops from armoured Humvee patrol vehicles they had captured from the Iraqi army and painted white, spray-painting Mahdi Army logos on it. Other government armoured vehicles were shown as smouldering wrecks.

The Iraqi security forces have also been beset by desertions, from police units acknowledged to be militia-infiltrated and from some army outfits believed to be better insulated against their influence.

“We did not expect the fight to be this intense,” said an officer from a special police unit drafted into Basra from Baghdad, recalling being pinned down by Mahdi Army mortar fire, where 4 men from his unit were killed and 15 wounded. “Some of the men told me that they did not want to go back to the fight until they have better support and more protection,” said the officer.

Basra residents reported that militiamen had attacked the house of a senior army officer from Basra, shooting his bodyguards. The officer was not home at the time. Gunmen kidnapped a senior government security spokesman from his Baghdad home the day before, killing three policemen guarding him then burning his house. And a senior police commander in Basra was bombarded with complaints from Iraqi soldiers that policemen loyal to the militia had opened fire on them, and that their families in Baghdad had received threatening text messages on their telephones.

But Major-General Ali Zaidan, the commander of Iraqi ground forces in Basra, said his troops had killed 120 “enemy” fighters and wounded about 450 since the start of the anti-militia campaign.

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