Security at the White House has been increased after a man with a knife scaled a perimeter fence and made it inside the building.

42 year-old Omar Gonzalez, who served in the US military, has been charged with unlawful entry.

Just hours later, another man was also detained, after he drove up to the gate of the White House and refused to leave.

Despite these threats, President Obama insists he still has confidence in the beleaguered agency's ability to protect him and his family.

Secret Service Director Julia Pierson ordered enhanced officer patrols and surveillance along the North Fence of the compound after the incident on Friday, which triggered a rare evacuation of the White House.

The agency said she had also ordered a comprehensive review of what happened.

"The president has full confidence in the Secret Service and is grateful to the men and women who day in and day out protect himself, his family and the White House," said White House spokesman Frank Benenati.

He said the White House expected Ms Pierson's review to be conducted "with the same professionalism and commitment to duty that we and the American people expect from the US Secret Service".

The presidential vote of confidence came as the agency sought to dispel growing concerns about security at the White House, one of the most heavily protected buildings in the world.