A bus carrying 35 Iraqi soldiers, part of military convoy under US escort, was bombed killing 20 servicemen, near the industrial city of Beiji, 250 kilometres north of Baghdad. No US casualties were immediately reported.
According to officials, three bombs also exploded near a police checkpoint and a gathering place for day laborers in one of Baghdad's main squares.
An Interior ministry official said the bombs went off early on Wednesday morning in Tayaran Square, downtown Baghdad, as workers gathered hoping to be employed for construction work.
The explosives were hidden in a garbage bag lying on the street.
Six people were found gunned down in various areas around Baghdad.
Kut municipal police later reported that gunmen had attacked a police checkpoint south of Baghdad killing 14 people, including six policemen.
A number of insurgents were also killed, an Interior Ministry official said, confirming the incident.
The attack happened late last night just 30 kilometres south of Baghdad.
Police in Kut also reported finding 18 bodies in the Tigris river, showing signs of torture and said had all been shot.
Insurgents killed
Iraqi police said that 15 insurgents and three police have been killed about 60 kilometres south of Baghdad.
Officers reported that insurgents fired rockets and mortars at Iraqi security forces in the town of Madaen drawing a counter-attack.
Four police officers and two civilians were wounded and 10 houses damaged in the fighting.
100th journalist killed since invasion
The interior ministry also announced the discovery of the body of a journalist from the Iranian television network, Al-Alam, in the Sunni west Baghdad neighborhood of Amiriyah.
The Iraqi Committee for Defence of the Media condemned the "kidnapping and assassination of the Iraq correspondent of Al-Alam, Adel al-Mansuri, the latest episode in the elimination of journalists by unidentified groups".
The press freedom group Reporters without Borders (Reporters sans frontiFres, RSF) announced that the latest casualty brings the "terrifying death toll" of media professionals killed in Iraq since the start of the US-led invasion in March 2003 to 100.
"No other war has been as murderous for the press since the Second World War," said the organisation, which called on the Iraqi government "to do its utmost to find those responsible for these atrocities and prosecute them."
The RSF added: "It is intolerable that nothing has yet been done to shed light on these killers who have become more and more common and that no measure has been taken to assure the protection of the professional media in Iraq."
The 20-year-old correspondent for the Iranian television station Al Alam was abducted in front of his Baghdad home on Sunday and his body was found on Tuesday.
Violence continues
Six weeks after a security crackdown was declared in Baghdad, violence continues unabated and thousands of US troops have been redeployed to the capital in a bid to boost security.
Wednesday’s dead included 20 Iraqi troops, a US soldier and a British soldier.
The recent surge of violence, blamed on sectarian rift between the Shiites and Sunnis and ordinary criminals, is being seen as a greater threat to the government of Prime Minister Nouri al-Maliki than the anti-government, anti-US Sunni insurgency, which had erupted after the fall of Saddam Hussein in March 2003.
The US military is moving at least 3,700 soldiers from Mosul to Baghdad and is gearing up for a new security operation to wrest control of the capital from Shiite militias, Sunni insurgents, kidnap gangs, rogue police and freelance gunmen.
US officials have described the Baghdad campaign as a "must-win" for al-Maliki, whose government has struggled to curb the rise in violence since it took office May 20. American troops will work alongside US-trained Iraqi forces.
Shiite march
Thousands of Shiite civilians charged with guarding neighbourhoods in Iraq have marched through Baghdad demanding an end to the sectarian violence.
The crowd included members of the Badr Organisation one of the armed Shiite groups that Sunni Arabs accuse of running militia death squads,a charge they deny.
The Prime Minister, whose reconciliation plan has failed to reduce sectarian bloodshed, has promised to disband the militias many fear will push the country into civil war.
Civil war 'more likely'
Meanwhile Britain's outgoing ambassador to Iraq has warned that civil war is the "more likely" outcome there than a transition to
stable democracy, according to details obtained by the BBC.
William Patey reportedly told British government ministers in a
confidential memo that Iraq was likely to break-up along ethnic lines because of the continuation of sectarian violence.
The ambassador made the assessment in his final telegram - which the BBC said it had seen - before leaving the Iraqi capital last week.
It was addressed to Prime Minister Tony Blair and senior ministers,
including the foreign and defence secretaries plus military top brass, it added.