LONDON — Allegations of prisoner abuse and civilian killings in Iraq from a cache of leaked U.S. secret military documents are extremely serious and must be investigated, a top British official said Sunday.

Deputy Prime Minister Nick Clegg told BBC television that the accounts of violence in Iraq “are distressing to read about and they are very serious.”

Whistleblowing website WikiLeaks has published almost 400,000 U.S. military logs, mainly written by soldiers on the ground, detailing daily carnage in Iraq since the 2003 U.S.-led invasion: detainees abused by Iraqi forces, insurgent bombings, sectarian executions and civilians shot at checkpoints by U.S. troops.

Iraq Body Count, a private British-based group that has tracked the number of civilians killed since the war started in March 2003, said it had analyzed the information and found 15,000 previously unreported deaths in the WikiLeaks documents released Friday.

Although the documents appear to be authentic, their origin could not be independently confirmed. The Pentagon has condemned the leak, as has Britain’s Ministry of Defense, which said it could put soldiers’ lives at risk.

Clegg said it was not for Britain to tell the U.S. how to respond, but that any allegations of abuse by British troops “are extremely serious and need to be looked at.”

“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,” he said.

Clegg’s Liberal Democrat party opposed the invasion of Iraq, and he has called the war illegal. His party, in opposition when the war began, is now part of Prime Minister David Cameron’s Conservative-led ruling coalition.

The Guardian newspaper has examined the files in detail and said it found two cases in which Iraqis reported being abused by British troops.

Britain is currently holding an official inquiry into mistakes made by British officials in the build-up and aftermath of the invasion of Iraq. It is due to issue a report later this year.