BAGHDAD, Iraq (AP) _ Insurgents blew up a small Shiite mosque northeast of Baghdad on Sunday, while police reported the discovery of nearly 40 bodies in several neighborhoods of the Iraqi capital, evidence of fresh sectarian killings. The U.S. military reported the death of three American soldiers.

The status of the crew of a U.S. helicopter that crashed Saturday southwest of Baghdad remained unclear.

The violence came as Secretary of State Condoleezza Rice and British Foreign Secretary Jack Straw made a surprise visit to press Iraqi politicians to speed up the formation of the government.

In Baqouba, 35 miles northeast of Baghdad, gunmen planted explosives around the small Guba Shiite mosque and blew it up, police said. No casualties were reported. Three stores selling music CDs also were bombed.

Roadside bombs targeted U.S. convoys in Ramadi, west of Baghdad, and the northern city of Mosul, but there were no reports of American casualties. Gunmen assassinated a Sunni Arab sheik, Abdul-Minaam Awad, in his village of Zobaa 40 miles west of Baghdad, a Sunni clerical association announced.

A prominent Sunni lawmaker in Baghdad, meanwhile, said his brother disappeared last week in a possible kidnapping. Saleh al-Mutlaq said his brother, Taha, went missing while driving north out of Baghdad to Salahuddin province. Al-Mutlaq is the head of the Iraqi Front for National Dialogue party.

``We haven't heard any solid information about who could have been behind this operation,'' said al-Mutlaq, whose brother belongs to his political party. ``I think this may be a political issue.''

The bodies found in Bagdad were all handcuffed and had been shot in the head or chest, said police Maj. Falah al-Mohammedawi. They apparently were victims of revenge killings between Sunni and Shiite Muslims.

Also Sunday, six insurgents died while manufacturing a homemade bomb inside a house in Madain, about 15 miles southeast of Baghdad, police said.

Two American soldiers were killed by a roadside bomb while on patrol in central Baghdad late Saturday, the U.S. military said. Another soldier from the 101st Airborne Division died Thursday from non-battle related injuries suffered in northern Iraq. No names were released.

Elsewhere, the U.S. military also said joint U.S.-Iraqi troops killed four insurgents and wounded another Saturday after two failed attacks near Balad, 50 miles north of Baghdad.

U.S. authorities said that Air Force F-16s and Navy F/A-18s provided close air support to U.S. and Iraqi forces in clashes Saturday with insurgents in six areas of northern, central and western Iraq.

The helicopter crash was the first since three went down in a 10-day period in January, killing a total of 18 American military personnel. At least two of the helicopters were shot down.

A U.S. statement said the helicopter went down about 5:30 p.m. Saturday during a combat patrol southwest of the capital but gave no further details. The statement did not identify the type of helicopter.

Rice and Straw said they came to Iraq to prod the country's struggling leaders to end nearly four months of wrangling and form a new government.

``We're going to urge that the negotiations be wrapped up,'' Rice said as she and Straw flew overnight to the Iraqi capital for meetings with the current interim government and ethnic and religious power brokers.

Straw said the choice of leaders is up to Iraqis alone, but neither he nor Rice disguised the blunt nature of their mission.

``There is significant international concern about the time the formation of this government is taking, and therefore we believe and we will be urging the Iraqi leaders we see to press ahead more quickly,'' Straw said.

Prime Minister Ibrahim al-Jaafari faced more pressure to step aside as the Shiite bloc's nominee for a second term. Talks among Shiite, Sunni and Kurdish leaders have stalled, in part because of opposition to al-Jaafari's nomination by the Shiite bloc.

Shiite legislator Jalal Eddin al-Sagheer was the latest to call for al-Jaafari to withdraw his nomination, saying the prime minister no longer had the acceptance of Iraqi parties and the international community.

``There is no other way out of the government formation problem,'' said al-Sagheer, a member of the United Iraqi Alliance and of the Supreme Council for the Islamic Revolution in Iraq.

Further delays could ``lead to more bloodshed,'' he added.

On Saturday, Qassim Dawoud was the first Shiite politician to join Sunnis and Kurds in publicly calling for a new Shiite nominee. Shiites politicians get first crack at the prime minister's job because they are the largest bloc in parliament.

U.S. officials believe formation of a government of national unity would be a major step toward calming the insurgency and restoring order three years after the U.S.-led invasion toppled Saddam Hussein. That would enable the U.S. and its coalition partners to begin withdrawing troops.

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Associated Press writers Sinan Salaheddin, Qassim Abdul-Zahra, Sameer N. Yacoub, and Mariam Fam in Baghdad contributed to this report.