British police believe they have arrested the main suspects in last week's Al-Qaida-style bomb plot, some of whom appeared in intelligence databases on radical Islamists, sources close to the investigation said yesterday.

The terror threat level was reduced yesterday night from "critical" to "severe" after no intelligence suggest any imminent danger.

Prime Minister Gordon Brown ordered a review of recruitment to Britain's state-run health service after security sources said all of the eight people arrested, including one in Australia, were doctors or have medical links.

Two are Indians and the rest are from the Middle East.

"I have asked ... the new terrorism minister to conduct an immediate review as to what arrangements we must make in relation to recruitment to the NHS (National Health Service)," Brown told parliament yesterday.

A security source said the MI5 intelligence agency had discovered fragments of information on some of the suspects in its databases on suspected radical Islamists. This had helped the investigation.

While no evidence has emerged that medical expertise was central to the plot, the alleged involvement of doctors has caused disquiet in Britain, where nearly 40 percent of registered doctors are foreign-trained.

Security analysts said the idea that militant Islamists could be working in hospitals, with potential access to dangerous biological or radiological substances, was alarming, even if no such materials were involved in this case.

"If all of these doctors are involved in this cell, that is very disturbing. That is a new dimension entirely for the security services," said M.J. Gohel of the Asia-Pacific Foundation in London.

A British Anglican cleric in Baghdad said he had received a veiled warning from an Al-Qaida leader while in Amman in April that attacks were planned against Britain and America and that "the people who cure you will kill you" - with hindsight, a possible reference to doctors.

Canon Andrew White told the Times newspaper he passed the warning, but not the actual words, to a Foreign Office official.

A police source said detectives believed they had now arrested the main potential attackers in a plot that Brown - in office for only one week - has said may be linked to Al-Qaida.

Police said a British counter-terrorism officer was en route to Australia to help detectives there question an Indian doctor detained on Tuesday while about to fly out of the country.

Detectives were questioning six people held in London. A seventh man arrested in Scotland after Saturday's attack on Glasgow airport remains ill in hospital with severe burns.

(China Daily via agencies July 5, 2007)