A security alert has been declared at Britain's House of Commons, the police said on Tuesday.
A police spokeswoman didn't say if the building had been evacuated or what caused the alert. Another spokesman said the building had been sealed and no one was being let in or out.
London has been on edge since Thursday's bombing attacks.
On Monday, the police briefly closed several streets where most government offices are located, including Parliament,
the Foreign Office and Prime Minister Tony Blair's 10 Downing Street office after a suspicious package was found, but it contained no explosives.
Police evacuated the King's Cross subway station for a while, but that too was a false alarm.