An international human rights group is urging Britain to investigate its role in the torture of terrorism suspects in Pakistan.

Human Rights Watch says the government was aware that Pakistani officials tortured five U.K. detainees but did not intervene.

The rights group says members of Pakistani intelligence agencies have corroborated its findings and backed its claims of British complicity. Quoting unidentified Pakistani sources, the group said in a report that British and American agents were "perfectly aware that we were using all means possible to extract information" from one suspect and were "grateful that we were doing so."

Britain's Foreign Office said Wednesday it "rejects in the strongest possible terms" claims it was complicit in torture.