by Salam Faraj

BAGHDAD (AFP) - Insurgents have launched a fierce assault on a US military outpost north of Baghdad, triggering a ѕυιcιdє car bombing that killed two American soldiers and wounded 17 more.

Earlier on Monday, more bombs gutted a Baghdad bus and hit a police patrol, adding 11 more bloodied corpses to the grim toll of Iraqi dead as rebel groups mount a savage challenge to the latest US and Iraqi security plan for the city.

In the western city of Ramadi, a car bomb killed 11 civilians, according to an Iraqi defence official.

The Americans were killed in what the military described as a "coordinated attack on a coalition force combat outpost" in Tarmiyah, some 30 kilometres (20 miles) north of the capital.

"Insurgents initiated the attack on the outpost with a ѕυιcιdє vehicle-borne improvised explosive device detonation," the US statement said. "The attack site has been secured and wounded soldiers have been evacuated."

The deaths brought to 3,132 the number of US servicemen and women who have died in
Iraq since the March 2003 invasion, according to an AFP tally based on
Pentagon figures.

The attack came as thousands of US and Iraqi troops continued a massive security operation in nearby Baghdad, where they are attempting to quell a sectarian war between rival Sunni and Shiite factions.

The Iraqi commuters were killed in the mixed but largely Shiite district of Karrada in the heart of the capital, one day after a double car bombing ripped through a crowd in a city market and killed more than 60 people.

In a second attack, a roadside bomb exploded in the path of a police patrol in the nearby district of Zafaraniyah. It killed three police and three civilians, and wounded 40 bystanders, according to a security official.

North of Baghdad, a ѕυιcιdє car bomber attacked a house in the Khazraj district belonging to an Iraqi army officer, Major Amer Nayif, killing five soldiers and wounding 10, police said.

South of Baghdad, one person was killed and seven wounded in a car bombing, while two car bombs detonated in Ramadi, one of them near a police checkpoint.

The attacks have been blamed on Sunni insurgents and appear to have been timed to embarrass US and Iraqi commanders as they put in place the much heralded Baghdad security operation.

"As displaced families return home peacefully, and hopes are raised by 'Operation Fardh al-Qanoon', criminal terrorists are not happy to see life returning to normal in Baghdad," said Prime Minister Nuri al-Maliki.

"Our dear people in Baghdad and across Iraq's provinces have chosen to go ahead with the political process despite sacrifices," he said.

"They are determined to stand by our armed forces to encourage them to drive out remnants of the Saddamists and Takfiris and all outlaws," he said, blaming Sunni extremists and supporters of executed dictator
Saddam Hussein.

Last week, Maliki formally announced the start of "Fardh al-Qanoon" -- Operation Imposing Law -- a plan that will see tens of thousands of US and Iraqi troops deployed around the capital to try to stem the bƖσσdshɛd.

"We knew they would strike back and try to get the most damage, the most casualties and the most effect in the media," said US spokesman Lieutenant Colonel Christopher Garver.

"We know that they try to foster the circle of sectarian violence, hoping for retaliation by the other side and trying to make it difficult for us to establish security," he said.

Before the blasts the operation had enjoyed a measure of initial success, and many Baghdadis remain hopeful that a turning point has been reached.

"Yesterday's bombings were the terrorists' remaining explosives. They will sooner or later run short of them. The plan has just started. We shouldn't expect too much," said Imad Salim, a 49-year-old Kurdish taxi driver.

Soldiers deploying to new security posts in flashpoint districts have met little organised resistance, although two US troops have been killed, and the number of corpses of murder victims found every day has dropped dramatically.

Shiite militias such as the Mahdi Army appear to have melted away, but the recent bomb attacks show that Sunni insurgent groups such as Al-Qaeda remain determined to sow chaos and undermine the US-backed government.

The United States is in the process of increasing its 20,000-strong force in Baghdad to 45,000 by May in a bid to assist and motivate a similar number of hard-pressed Iraqi security forces.

"This plan is going to take months," Garver warned.