Eight US soldiers died in separate bombing attacks across Iraq, and two in a helicopter crash, taking the May toll to 112 and making it the deadliest month for US troops since December, when the same number died.
The military did not say if the helicopter was shot down or had mechanical problems.
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Meanwhile, the UK confirmed on Tuesday that five British nationals had been abducted in the Iraqi capital by armed men in police uniforms from a government building.
"I can confirm that a group of five British nationals were abducted this morning at 08:50 UK time, which is 11:50 local time, in an incident at the finance ministry in central Baghdad," a foreign office spokesman said.
"Officials from the British embassy in Baghdad are in urgent contact with the Iraqi authorities to establish the facts and to try to secure a swift resolution."
Canadian-based security firm GardaWorld said four of those kidnapped were its employees and one was a client.
Police said about 40 armed men sealed off streets around the three-storey computer science building belonging to the finance ministry before they went inside.
Dozens of people were killed and scores injured in attacks across Baghdad on Monday as well.
The deadliest attack was a car bombing in central Baghdad near the Abdul-Qadir al-Gailani mosque, the city's largest Sunni mosque that Shia also revere, killing 24 people and injuring scores, police say.
Fighters carried out several other car-bomb and mortar attacks throughout the capital.
Police said three civilians were killed and 10 wounded by a car bomb in Zaafarniya district in southeastern Baghdad, and a roadside bomb killed two people and injured nine when it exploded under a parked car in the central Baghdad district of Bab al-Muadham.
Also on Monday, police said they had recovered 33 bullet-riddled bodies in different parts of Baghdad.
The bodies were handcuffed, blindfolded and showed signs of torture.
Separately, US forces announced they had rescued 42 Iraqi captives after raiding an alleged al-Qaeda prison camp north of Baghdad.
They said some of those freed showed signs of having been tortured for months.
Military officials said Sunday's operation was launched after a tip-off from local residents in Diyala province.
Many of the 42 civilians, including a teenager, showed signs of abuse including broken bones, bruises and heat injuries caused by dehydration.
Officials have refused to release details of the raid, citing security reasons.