London: Police were holding eight people on Tuesday, at least four of them foreign doctors, over a suspected Al Qaida plot against Britain that has triggered a manhunt stretching as far as Australia.

Click here to see the details of arrests (pdf)

One British security source said two of the suspects were Indian, the rest were Middle Eastern and "quite a few" were doctors - a contrast with recent British conspiracies led by "homegrown" militants, often with modest academic backgrounds.

Two of those arrested worked at hospitals in England, one was a doctor in Scotland and Australian police also detained an Indian doctor, Mohammad Haneef, under counter-terrorism laws. Police sources said the other suspects also had medical links.

Separately, Two men were arrested in an industrial park in northwestern England under the Terrorism Act on but a statement from Lancashire police said it was "too early to confirm whether or not these arrests are linked to recent events in London and Glasgow."

The discovery of two car bombs primed to explode in London's bustling theatre and nightclub district last Friday put a city already attacked by four suicide bombers in 2005 on edge.

When a fuel-laden jeep rammed into a Scottish airport the next day, Britain's threat level was raised to its highest level, "Critical" - meaning more attacks may be imminent.

A security source said it was "entirely speculative" for media to suggest the doctors formed an al Qaeda sleeper cell smuggled into Britain using their medical profession as cover.

"We don't know enough to say whether they were radicalized here or overseas, or how they met," he said.