LONDON, (Reuters) – A British official has said five Iranians arrested in Baghdad last month in a raid by U.S. forces were senior intelligence officers thought to be on a covert mission to influence the Iraqi government, the BBC reported.

Several Iranians — including two diplomats who were later released -were arrested by U.S. troops in the raid, which the BBC said occurred on Dec. 21 in the compound of SCIRI head Abdul Aziz al-Hakim, one of Iraq’s most powerful Shi’ite leaders. “There were five senior officers in various Iranian intelligence organisations,” the BBC’s Newsnight television programme, broadcast late on Thursday, quoted the unnamed official as telling it. “It was a very significant meeting. These people have been collared, relatively speaking, up to no good.”

Three intelligence officers had since been set free but the U.S. military continued to hold two others, the BBC said.

Britain’s foreign ministry declined to comment on the report. “We’ve always made clear it is vital that all Iraq’s neighbours support Iraq as it develops its own security and democracy,” a Foreign Office spokesman said. “Anything that undermines the Iraqi government is unhelpful and any Iranian links to armed groups in Iraq are unacceptable.”

British officials were quoted as telling the BBC that the raid produced some important intelligence in spite of failing to provide a “smoking gun” linking the Iranians to supplies of arms to Shi’ite militants who attack British troops in southern Iraq.

The U.S. State Department has said “a small number” of diplomats were among those detained in raids last month against Iranians suspected of planning attacks on Iraqi security forces, but they were turned over to Iraqi authorities and released.

Iran’s foreign ministry has said the diplomats had been invited by the Iraqi government. The BBC said the arrested men were in Iraq to hold high-level meetings with Iraqi Shi’ite factions. “There was discussion of whether the (Prime Minister Nuri al-) Maliki government would succeed, who should be in which ministerial jobs,” one British government source told Newsnight. “It was a very significant meeting. The fact of who some of the Iranians were is very significant.”