A bomb threat in central London has closed down The Mall, near Buckingham Palace. The coded warning, received by police, comes on the eve of the Queen’s visit to Ireland.

The bomb alert was sparked by a disturbed manhole cover, leading to the closure of The Mall and Carlton House Terrace, a Metropolitan Police spokesman said.

Roads around Northumberland Avenue were also closed in a second security scare while a bag was destroyed in a controlled explosion. However police said the bag was no longer deemed suspicious.

Security remains tightened in the capital after the “non-specific” threat was issued to authorities last night.

A Scotland Yard spokesman said: “A bomb threat warning has been received relating to central London today. The threat is not specific in relation to location or time.”

Eight vehicles from the ambulance service, including a command and control unit, were parked on the Mall in response to the bomb threat.

The threat comes a day before Queen Elizabeth makes a historic visit to Ireland, although it is not certain if it came from Irish republican dissidents.

Police are asking the public to be vigilant.