The church attacks came amid a flurry of other bombings in and around the two cities that killed at least 10 Iraqis and an American soldier. The U.S. military confirmed two other explosions in Baghdad in the evening, but their target was not immediately clear.

The church attacks in Baghdad appeared to be car bombs. The two blasts exploded just minutes apart outside two nearby churches one Armenian and one Catholic in the Karada neighborhood.

Massive plumes of black smoke poured into the evening sky over the city as firefighters struggled to put out flames leaping from the front of the Armenian church and several blackened cars.

"I saw injured women and children and men, the church's glass shattered everywhere. There's glass all over the floor," said Juliette Agob, who was inside the Armenian church during the first explosion.

At nearly the same time, two blasts struck outside a church in Mosul and a third blast hit a bridge, Iraqi officials said. There was no immediate word on casualties.

Meanwhile, a tribal leader mediating with kidnappers for the release of seven kidnapped truck drivers said talks had hit a dead end, denying claims by the Kenyan government that the men had been freed.

"The two sides were unable to reach an agreement, I don't know what's going to happen now," said Sheik Hisham al-Dulaimi. He said there was no longer contact with the hostage-takers. The captives "have not been released," he said.

The three Kenyans, three Indians and one Egyptian have been held since July 21, and their kidnappers calling themselves "The Holders of the Black Banners" have threatened to kill them unless the Kuwaiti company that employs them withdraws from Iraq.

The company, Kuwait and Gulf Link Transport Co., had been working with al-Dulaimi to win the hostages' release. Al-Dulaimi did not give details on the breakdown in talks.

Militants in Iraq have kidnapped more than 70 foreigners in recent months in an effort to push countries out of the U.S.-led coalition that invaded Iraq and toppled Saddam more than a year ago.

At the same time, the campaign of violence waged by insurgents since the fall of Saddam Hussein has not waned, despite last month's transfer of sovereignty from the U.S. occupation authority. About 160,000 coalition troops, mostly Americans, remain in Iraq.

In Fallujah, U.S. forces briefly entered the edge of the city overnight in fighting that shook the area with huge explosions. Marines were firing tanks at insurgents who had opened fire on them with mortars, machine-guns and rocket-propelled grenades, the military said.

Coalition aircraft also dropped guided bombs on a building in an industrial zone from which gunmen were firing, the military said.

At least 12 people were killed and 39 wounded in the fighting, a Health Ministry official said on condition of anonymity. The U.S. military said it had killed 10 assailants during the clashes.

In a suicide bombing Sunday morning in Mosul, a white four-wheel drive vehicle sped toward the Summar police station at around 8 a.m, and a police guard opened fire and killed the driver, the police and U.S. military said. The vehicle crashed into the concrete barriers around the station and exploded, killing five people including three police and wounding 53 people, according to the al-Salam hospital.

A roadside bomb hit a 1st Infantry Division patrol in Samarra, a hotbed of violence 60 miles northwest of Baghdad, killing a U.S. soldier and wounding two others. The death brought to at least 910 the number of U.S. service members have died since the beginning of military operations in Iraq in March 2003.

A bomb killed two civilians and wounded at least two others on Abu Nawas street, an avenue in central Baghdad along the eastern banks of the Tigris River. Another bomb on a southern Baghdad highway killed one man Sunday and injured two others.

Two policemen were killed and three injured when their truck was attacked by insurgents in Haswa, 40 miles south of Baghdad on Saturday, police Lt. Ali Aubeid said.

Also Sunday, U.S. authorities released 128 prisoners from a detention camp at Abu Ghraib, west of Baghdad, bringing the total number of detainees released since January to 7,000.

A Kenyan government spokesman, Alfred Mutua, said earlier Sunday that the seven truck drivers held in Iraq had been freed. But after al-Dulaimi's denials, Mutua backed off, syaing their release was not confirmed.

Two Turkish companies said Sunday they might stop doing business in Iraq in order to secure the release of two Turkish truck drivers whose abduction was announced in a videotape broadcast on Al-Jazeera television Saturday.

In the video, the Tawhid and Jihad group of Jordanian militant Abu Musab al-Zarqawi threatened to behead the men in 48 hours unless the companies Oztur International Transportation and Kahramanli Transportation leave Iraq.

The two companies said they might comply. "The important thing for us is the return of both drivers unharmed," Omer Ozturk, an official of the Oztur International Transportation, said in reading a joint statement. The drivers were identified as Abdulrahman Demir and Sait Unurlu.