Police have arrested a man who witnesses say "ran up" to the Queen's coffin as it lay in state at Westminster Hall. 

Onlookers said the man tried to touch the Queen's coffin.

"Some person decided they were going to push my seven-year-old niece out the way, run up to the coffin, lift up the standard and try to do I don't know what," witness Tracey Holland said.

"She was grabbed out the way and the police had him within two seconds."

The Metropolitan Police said at about 10pm local time officers from the Parliamentary and Diplomatic Protection Command detained a man in Westminster Hall after a disturbance.

Just hours before, the Queen's four children had stood vigil at her coffin. 

AP