BAGHDAD (Reuters) - Iraq's Shiite Islamists were confirmed in power by election results on Friday that gave them a near-majority and paved the way for negotiations to begin on a national unity government promoted by the United States.

With Baghdad all but sealed off by security forces on alert for attacks by Sunni Arab rebels, two civilians were killed in one of several bomb attacks on U.S. and Iraqi patrols.

In the Sunni bastion of Ramadi, insurgents fired rockets at U.S. bases; there was celebratory gunfire in the holy Shiite city of Najaf.

Troops and police blocked off roads between Baghdad and the restive provinces of Anbar, Salahaddin and Diyala and were also hunting kidnappers who threatened to kill an American journalist by a Friday deadline; leading Sunni Arab figures joined Jill Carroll's family and colleagues in calling for her release.

Despite angry reactions to the rejection of their complaints about the Dec. 15 vote, many Sunni political leaders, who boycotted last year's interim assembly but now have a fifth of the 275 seats in the new parliament, are already discussing places in a grand coalition with the Shiites, Kurds and others.

"Now that the results are out we're going to start serious talks in Baghdad to form a national unity government based on these results," Alliance official Abbas al-Bayati told Reuters, adding that meetings could begin as soon as Saturday. Sunni politician Hussein al-Falluji, accusing U.S. officials of pressuring international monitors to reject Sunni allegations of massive fraud, said negotiations would be tough but would happen: "We are not happy with these results," he told Reuters.

"That means forming a new government will be very difficult."

The U.S. ambassador joined calls for Iraq's sectarian and ethnic communities to come together after the results to form a government including all groups; Washington hopes consensus can staunch the bloodshed and let it bring its U.S. troops home.

The final results, which parties have two days to challenge, were in line with a profusion of earlier provisional data.

They gave the Alliance 128 seats, 10 short of retaining the slim majority it had in the interim assembly elected a year ago in a vote boycotted by most Sunnis, who then won just 17 seats.

The main Kurdish bloc won 53 seats, down sharply on much higher national turnout of 78 percent, compared to 58 percent; two Sunni groups shared 55 seats -- winning 44 and 11 places.

Former Prime Minister Iyad Allawi's secular list, looked on favourably by U.S. officials, has 25 seats, and seven other groups, comprising Kurds, Sunnis, Shiites, ethnic Turkmen and Christian and Yazidi sects won between one and five seats each.

As her captors' deadline neared, with U.S. forces rejecting their demand that women prisoners be freed, influential Sunni leaders joined Carroll's family in urging her release.

After heavy media coverage in the United States, Adnan Dulaimi called for the release of 28-year-old Carroll by kidnappers who set a 72-hour ultimatum in a video on Tuesday.

"Release this journalist who strived for Iraq, defended Iraqis and condemned the war in Iraq," Dulaimi, whose office Carroll had just left when she was kidnapped on Jan. 7, told a news conference. Her translator was killed in the ambush.

In Cairo, the influential Muslim Brotherhood also issued a public call for the journalist to be freed.

U.S. officials insist there are no plans to release women, despite remarks to the contrary by the Iraqi Justice Ministry. The reporter's father, Jim Carroll, addressed her captors on Arabic satellite television Al Jazeera: "My daughter has no influence, she doesn't have the power to free anyone."

Echoing calls from the UN envoy and from the international monitors, the U.S. ambassador to Iraq, Zalmay Khalilzad, issued a statement welcoming the monitors' report, saying: "Once the final election results are announced, Iraq's political parties and their leaders must come together to reinforce their commitment to democratic principles and national unity."

U.S. and Iraqi forces have been bracing for violence around the results, both from local Sunni nationalists who had observed a ceasefire in the hope of a strong showing in the election and from al Qaeda-linked Islamists opposed to U.S.-backed democracy.

A senior Iraq military source told Reuters security forces had foiled an insurgent plot to mount a mass assault on the Baghdad headquarters of Alliance leader Abdul Aziz al-Hakim, a hate figure for many Sunnis suspicious of his ties to Iran.

Insurgents killed at least 22 people in two simultaneous bomb blasts in central Baghdad on Thursday.

Police north of the capital fear as many as 34 recruits may have been killed on Tuesday after gunmen ambushed a bus. A wounded survivor said 14 were certainly shot dead in a well. Police said they had found seven bodies in the area so far.

There was no word on the fate of Carroll or other foreign hostages, among thousands of people abducted for money or political goals since the U.S. invasion of 2003.