Two bombs exploded near a Shia Muslim mosque in Baghdad's al-Shuli district, killing at least 15 people, a police official said.
The official said 40 people were also wounded at the Ahl al-Bait mosque. A witness said he saw many ambulances rushing to the scene, a crowded market area.
Earlier on Sunday, two powerful car-bomb blasts in the northern Iraqi town of Tikrit killed at least six people and injured 26.
The first bomb exploded outside a police academy in the hometown of ousted president Saddam Hussein just after 8am (0400 GMT) as recruits were preparing to travel to Jordan for training, police Colonel Abd Allah Ali said.
The second blew up 20 minutes later outside a nearby army liaison office.
Police casualties included four dead and 18 wounded, Ali said.
Meanwhile, reports say Iraq's leading political figures will announce a new government within days, perhaps as early as Monday.
Legislators and people involved in the negotiations said, however, that no one from caretaker prime minister Iyad Allawi's party will be in the new government.
An Allawi aide said he would back
the government from outside
"Allawi will take no part; his party will have no ministries," a senior official involved in the talks said on Sunday.
He added the decision was taken after a round of negotiations on Saturday that lasted more than 10 hours.
Separately, Vice-President Ghazi al-Yawir held a meeting with Sunni Arab notables and set up a five-man committee with himself as its head, Aljazeera reported.
The committee was authorised to hold negotiations on the participation of Sunni Arabs in the new government.
Iraqi journalist Hamid Hadid was quoted on Sunday by Aljazeera as saying the committee had already met Prime Minister-designate Ibrahim al-Jafari to discuss Sunni Arab participation in the new government.
Hadid said the business of forming a new Iraqi govenment had been further complicated by the US Defence Secretary Donald Rumsfeld's recent statement cautioning against purges in the government's security apparatus.
The statement is seen by some observers as Washington's wish that the powerful defence and interior portfolios, now with Allawi's group, should remain untouched.
Two car bombings on Sunday in
Tikrit targeted police recruits
This would to all intents foil any Shia plans to effect shake-ups in these ministries.
The question of who should assume the crucial two portfolios has become one of the most controversial and difficult ones facing the interim government.
If the cabinet is not appointed by early next month, Prime Minister-designate al-Jafari could be forced to step down.
On the other hand, if a cabinet is presented to parliament on Monday, it is expected that the Shia alliance will take 17 of an expected 32 ministries, including the Interior Ministry.
The Kurds are expected to receive eight posts and the Sunnis the remainder.
Female members of the national
council attending a session
It remains unclear who will get the defence and interior portfolios and the coveted Oil Ministry.
Under Iraq's interim constitution, the 275-seat assembly must approve the prime minister and his cabinet by a simple majority
The Shia-led United Iraqi Alliance took 146 of the 275 seats in parliament, while the main Kurdish bloc took 77.
But both groups want to include the Sunni Arabs in a new government in an effort to wean the former elite away from anti-US fighters and into the political mainstream.
On Saturday, Allawi urged the legislators to "safeguard Iraq's march towards democracy" by ending the standoff.
In other developments, Aljazeera has learned that the leader of the reconciliation and liberation bloc and a member of the Iraqi interim national assembly, Mishan al-Juburi, has survived an attempt on his life using a booby-trapped car.
The incident took place at the southern entrance of Baiji town, north of Baghdad, on Sunday. Four people were wounded, among them two of al-Juburi's personal guards.
Legislators say a cabinet may
be formed as early as Monday
On the same day, a bomb killed a US soldier in Baghdad, the US military said.
A US sailor was killed by a bomb during combat operations on Saturday in Falluja, about 50km west of Baghdad, and a US soldier was killed when a bomb exploded near a military convoy near al-Haswah, west of Baghdad.
Separately, US forces said they had arrested four more suspects in the recent shooting down of a civilian helicopter, bringing the number apprehended to 10.
All 11 passengers and crew were killed, including one shot by anti-US fighters.
US soldiers from Task Force Baghdad, working with Iraqi
security forces, detained the suspects in the past 24
hours, a military statement said on Sunday.