(Updates with more trials of U.S. soldiers)

By Ibon Villelabeitia

BAGHDAD, Oct 18 (Reuters) - Eleven U.S. soldiers were killed in Iraq, the U.S. 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 U.S. troops killed in October so far, an exceptionally high toll that is likely to bring renewed attention to the Iraq war in the run-up to U.S. 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 U.S. troops have died since the 2003 invasion. Many more Iraqis have been killed.

The U.S. military announced that eight U.S. soldiers will face court-martials, including four over the rape and murder of an Iraqi girl and the killing of her family in Mahmudiya.

Since the revelation of probes into the killings of 24 people at Haditha in November, U.S. commanders are cracking down on rogue soldiers in a bid to regain the trust of ordinary Iraqis after three years of growing resentment.

With two weeks before the end of October, the pace will make it the deadliest month for U.S. forces since January 2005. All but one of the 11 soldiers died on Tuesday. Commanders blame the toll on aggressive patrolling in Baghdad, the epicentre of sectarian violence threatening to plunge Iraq into civil war.

After falling to 43 in July, the U.S. toll rose to 65 in August and to 71 in September. U.S. 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 U.S. 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 U.S. Secretary of State James Baker, drafting a report on possible alternatives to current U.S. policy in Iraq, has said there is no "magic bullet" to solve Iraq's problems.

AL QAEDA GUNMEN IN RAMADI

In a new show of force, dozens of al Qaeda-linked gunmen took to the streets in Ramadi on Wednesday 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 a message of defiance from the Mujahideen Shura Council, a Sunni militant group led by al Qaeda in Iraq.

In Baghdad, the U.S. military acceded to a request by the Iraqi government and released a senior aide to a pro-government Shi'ite cleric and militia leader detained on Tuesday.

The move came despite mounting pressure from U.S. 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 U.S. military forces during a raid on his Baghdad house early on Tuesday along with four men.

U.S. military spokesman Lieutenant Colonel Christopher Garver would not say if Saedi, head of Sadr's office in a Baghdad neighbourhood, had been detained on suspicion of any crime.

In background briefings and in private conversations, U.S. commanders and U.S. government officials have expressed growing frustration at Maliki's inaction to move against militias.

Maliki, a Shi'ite, 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 U.S. forces, controls a large bloc of seats in parliament, which makes Maliki dependent on Sadr's support.

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