LONDON - Police said on Saturday they were evacuating thousands of people from the center of Birmingham, Britain's second city, after receiving intelligence of a threat.
The security alert came two days after bombings by suspected Islamist militants that killed more than 50 people in London.
A police spokeswoman said she could not confirm media reports that police had carried out a series of controlled explosions on suspect packages.
A Sky News reporter said she had seen two bomb disposal vans traveling past at high speed, and a police helicopter was hovering overhead.
"West Midlands police... are now closing down the Broad Street entertainment zone and asking people to leave Birmingham town center and go home," a police spokesman said.
"Our inquiries are ongoing. We're not going into the nature of the threat. ... Clearly we're taking it quite seriously."
He estimated up to 30,000 people could be in the area being cleared, which is packed with nightclubs, bars and restaurants.
No arrests had been made, the spokesman said. "What we're talking about is warning the public and making sure people are safe."
Police said the evacuation was proceeding smoothly.
"We tried to get into the center of Birmingham this evening but were turned back by the police. They wouldn't tell us any reason," a local resident, Phil Debenham, told Reuters.
He said people were leaving the area calmly.
The operation was by far the biggest of several security scares in Britain on Saturday in the wake of Thursday's attacks on London's transport system.
Police have warned the bombers may still be at large and could strike again.
Feeds