A roadside bomb killed four American soldiers in Baghdad, the US military said on Monday.
The military had earlier reported the deaths of two other US soldiers on Sunday and one on Saturday.
One day after Mr Maliki won a promise from tribal leaders to rein in Iraq's violent factions, bombers carried out deadly attacks across the country, with four attacks targeting the northern Kurdish minority that left 15 people dead.
This latest savagery was a blow to Mr Maliki's authority on a day in which he once again insisted that Iraq was not slipping into civil war.
"The violence is on the decrease, and our security ability is increasing," Mr Maliki said in an interview with CNN television. "I want to assure he who loves Iraq that Iraq will never be in a civil war."
Shortly after the interview was broadcast, gunmen stormed a market in Khallis, a mainly-Shi'ite town north of Baghdad, and sprayed automatic fire indiscriminately into a crowd, killing 14 people and wounding 25.
Kurds targeted
Earlier, two near simultaneous suicide car bomb attacks on Kurdish targets killed 10 and wounded 50 more in the ethnically mixed northern Iraqi city of Kirkuk.
One attack hit a religious shrine owned by the family of Iraq's Kurdish President Jalal Talabani, the other the home of a Kurdish police chief, Colonel Ahmed Abdallah's, whose son was among the dead.
Both attacks took place in the Iskan district, a stronghold of Talabani's tribe and of his party, the Patriotic Union of Kurdistan (PUK) in Kirkuk, an oil-rich city which is claimed by both Arabs and the Kurds.
A third suicide car bomber had blown himself up earlier near the PUK office in Kirkuk, killing one guard and wounding 16 party members.
In yet another attack on Kurds, four Kurdish policemen - including a young police academy graduate on his way to meet his fiancee to arrange their wedding - were killed by alleged Sunni extremists, police said.
Insurgents also targeted Baghdad, the southern city of Basra and Diyala province - a hotbed of fighting between rival sectarian death squads - where at least 26 people, including the 14 mowed down in the market, were killed,
Six civilians, including two women, were killed when a booby-trapped roadside bomb exploded in a crowded street in Khallis, north of Baquba, the capital of Diyala.
Six others were killed in a spate of shootings around Baquba, while two truck drivers and a former policeman were kidnapped. Two corpses were also found near the city.
Attacks in Baghdad
Baghdad, where a major security operation has been in place since July, saw some major attacks on Sunday leaving at least 11 dead.
A suicide bomber ploughed an explosives-laden van into the parking lot of the state-owned Al-Sabha newspaper, detonating his deadly cargo after coming under fire from security guards.
"Two people were killed and 25 others wounded. They all were employees of the newspaper," Karim al-Rubaiya, Al-Sabah's technical editor.
The blast devastated the front of the two-storey concrete office building and scattered the blackened wreckage of a fleet of cars across the car park.
An apparent suicide attack on a bus killed at least five people and wounded 15 in the busy commercial heart of the capital, near the Palestine Hotel, which was once famous as a centre for the international media.
Gunmen also killed four of former Sunni Deputy Prime Minister Abd Mutlaq al-Juburi's bodyguards in an ambush on their car in Baghdad's Ameriyah neighbourhood.
In the southern Shi'ite city of Basra, a suicide bomber on a motorbike killed seven people and wounded 10 more in an attack on a marketplace.
Some 10,000 Iraqis have been killed in the last four months alone in unrelenting attacks by Sunni and Shi'ite extremists on each other's communities, as well as bombings and shootings by Sunni Arab insurgents.
More than 2,600 American military personnel have died since the beginning of the Iraq war in March 2003.