LONDON - A man with a knife who assaulted two police officers outside Buckingham Palace on Friday night has been arrested, British police said.The officers suffered minor injuries and did not need to be treated at hospital. The man was arrested on suspicion of grievous bodily harm and assault on police near to Queen Elizabeth's London residence.Britain has been hit this year by four militant attacks in which 36 people were killed, and the country's threat level is at severe, meaning an attack is highly likely.Footage on Sky News showed emergency vehicles lining the street outside the palace. A Metropolitan Police spokeswoman said she was unable to comment at this stage on the motivation for the incident.A Reuters witness near the scene said police had cordoned off a wide area around the palace for security."The man was stopped this evening, Friday 25 August at approximately 20:35 hours (1935 GMT) by officers at the Mall outside Buckingham Palace in possession of knife," the police said in a statement."During the course of detaining him, two male police officers suffered minor injuries to their arm."