Allegations of killings, torture and abuse in Iraq contained in leaked US military logs "need to be looked at", Nick Clegg said today.

The deputy prime minister said any suggestion that the rules of war had been broken or torture had been condoned were "extremely serious".

The almost 400,000 secret US army field reports show two cases of alleged involvement of British troops in the abuse of detainees.

Clegg did not rule out the possibility of an inquiry into the actions of British forces in Iraq, but said it was up to the US administration to answer for the actions of its forces.

His comments contrasted with a statement from the Ministry of Defence yesterday, which warned that the posting of classified US military logs on the WikiLeaks website could endanger the lives of British forces.

Clegg told BBC1's The Andrew Marr Show: "We can bemoan how these leaks occurred, but I think the nature of the allegations made are extraordinarily serious. They are distressing to read about and they are very serious. I am assuming the US administration will want to provide its own answer. It's not for us to tell them how to do that."

Asked if there should be an inquiry into the role of British troops, he said: "I think anything that suggests that basic rules of war, conflict and engagement have been broken or that torture has been in any way condoned are extremely serious and need to be looked at."

He added: "People will want to hear what the answer is to what are very, very serious allegations of a nature which I think everybody will find quite shocking."

Vince Cable, the business secretary, also said allegations of abuse should be investigated and criticised the way in which they were leaked. He told Sky News Sunday Live: "The Liberal Democrats were strong opponents of the Iraq war and we do feel vindicated by what's happening."

He added: "I think there have been several investigations already but I think, clearly, if there have been abuses taking place they need to be investigated – that's obvious enough."

British involvement in the alleged torture and unlawful killing of Iraqi civilians may also be the subject of legal action. Lawyers said the reports embroiled British as well as US forces in an alleged culture of abuse and extrajudicial killings in Iraq.

Phil Shiner, of Public Interest Lawyers, appearing alongside the WikiLeaks founder Julian Assange at a press conference in London yesterday, said some of the deaths documented in the reports may have involved British forces and could now go through the UK courts. The Iraq war logs, Shiner said, indicated that British as well as US commanders were likely to have ignored evidence of torture by the Iraqi authorities, contrary to international law.

"Some of these deaths will be in circumstances where the UK have a very clear legal responsibility. This may be because the Iraqis died while under the effective control of UK forces – under arrest, in vehicles, helicopters or detention facilities," he said.

The Ministry of Defence said the publication of the records was reckless and put the lives of British military personnel in danger, adding that it investigated any allegations made against British troops. It said: "There is no place for mistreatment of detainees. Any civilian casualty is a matter of deep regret and we take any incidents extremely seriously."

As Assange defended the decision to disclose the documents – saying it was of "immense importance" to reveal the truth about the conflict – the UN warned that if the logs pointed to clear violations of the UN convention against torture, Barack Obama's administration had a clear obligation to investigate them.

Manfred Novak, the UN special rapporteur on torture, said: "President Obama came to power with a moral agenda, saying we don't want to be seen to be a nation responsible for major human rights violations." A failure to investigate credible claims of complicity in torture, Novak suggested, would be a failure of the Obama government to recognise US obligations under international law.

The US defence department condemned the WikiLeaks release, describing the documents as raw observations by tactical units, which were only snapshots of tragic, mundane events. Assange said the snapshots of everyday events offered a glimpse at the "human scale" of the conflict. He told the news conference his motive for the disclosure was "about the truth".

Iraq Body Count, a private British-based group that has tracked the number of Iraqi civilians killed since the war began in 2003, said its analysis of the logs had raised its total of civilian deaths from 107,369 to more than 122,000. IBC, which worked with WikiLeaks, said the war logs showed there were more than 109,000 violent deaths between 2004 and the end of 2009. They included 66,081 civilians, 23,984 people classed as "enemy", 15,196 members of the Iraqi security forces, and 3,771 coalition troops.

John Sloboda of IBC said: "They [the documents] show the relentless grind of daily killings in almost every town or village in every province."

WikiLeaks yesterday promised to publish 15,000 more documents about the war in Afghanistan.