Eleven US soldiers were killed on Tuesday, the US military said on Wednesday, in one of the sharpest spikes in attacks on American forces battling soaring sectarian violence and a Sunni Arab insurgency.
The bloodshed brings to at least 69 the number of US troops killed in October, an exceptionally high toll that is likely to bring renewed attention to the Iraq war in the run-up to US congressional elections in November.
President George W. Bush's popularity has been hurt by growing discontent over the war and his Republican Party risks losing control of Congress in the Nov. 7 vote.
At least 2,778 US troops have died since the 2003 invasion. Many more Iraqis have been killed.
With two weeks to go until the end of October, the pace will likely make it the deadliest month for US forces since January 2005. US commanders have attributed the rising toll to more aggressive patrolling in Baghdad, the epicentre of sectarian violence that is threatening to plunge Iraq into civil war.
After falling to 43 in July, the US toll rose to 65 in August and to 71 in September. US commanders, who have declared the fight for Baghdad the war's main effort, have conducted major security sweeps in the capital since August, massing neighbourhoods with troops to flush out militants.
Some 15,000 US troops in Baghdad are trying to curb death squads and other armed groups. Despite the crackdown violence has continued unchecked in Baghdad and other areas.
Former US Secretary of State James Baker, who is drafting a report on possible alternatives to current US policy in Iraq, has said there is no "magic bullet" to solve Iraq's deepening problems.

AL QAEDA GUNMEN IN RAMADI
Dozens of al Qaeda-linked gunmen took to the streets in Ramadi on Wednesday in a show of force to announce the city was joining an Islamic state comprising Iraq's mostly Sunni Arab provinces, Islamists and witnesses said.
Witnesses in Ramadi, the capital of western Anbar province, said gunmen dressed in white marched through the city as mosque loudspeakers broadcast the statement by the Mujahideen Shura Council, a Sunni militant group led by al Qaeda in Iraq.
Following a request by the Iraqi government, the US military released on Wednesday a senior aide of a pro-government Shia cleric and militia leader detained on Tuesday.
The move comes despite mounting pressure from US commanders and officials demanding that Prime Minister Nuri al-Maliki rein in militias and their networks, blamed for some of the worst sectarian violence gripping Iraq.
Sheikh Mazin al-Saedi, an aide to radical cleric Moqtada al-Sadr, had been detained by US military forces during a raid on his Baghdad house early on Tuesday along with four men.
"He has been released at the request of the government of Iraq," Lieutenant Colonel Christopher Garver, a spokesman for the US military told Reuters.
Garver would not say if Saedi, who heads Sadr's office in the Baghdad neighbourhood of Shula, had been detained on suspicion of any particular crime.
In background briefings and in private conversations, US commanders and US government officials have expressed growing frustration at Maliki's inaction to move against militias.
Maliki, has pledged to deal with militias but disbanding them could put him in a precarious situation because they are tied to political parties in his coalition.
Sadr, who heads the Mehdi Army militia that has launched two uprisings against US forces, controls a large bloc of seats in parliament, which makes Maliki dependent on Sadr's support.
In the worst violence against US forces on Tuesday, four soldiers were killed when their vehicle was struck by a roadside bomb west of Baghdad, the US military said in a statement. Three were killed and one wounded in northern Diyala province.
Previous spikes in US fatalities coincided with major American operations against Sunni insurgent bastions, including the November 2004 offensive in Falluja, near Ramadi.
In another development, a US military official said on Wednesday that four US soldiers face court martial over the rape and murder of an Iraqi girl and the killing of her family in their home in Mahmudiya.