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The Secret Service has erected a second fence between the White House and a thoroughfare popular with tourists, local residents and workers, days after a man scaled the main fence and entered the mansion through an unlocked door.

The Secret Service said the new fence created a "temporary buffer zone" while it reviewed its procedures.

The new barrier is a series of linked sections about a metre (3.2ft) high.

Omar Gonzalez, 42, is being held in connection with the Friday intrusion.

Authorities say he was carrying a 9cm (3.5in) knife and faces charges of unlawfully entering a restricted building carrying a "deadly or dangerous weapon".

Mr Gonzalez, an Iraq War veteran, was previously stopped by Virginia police in July. Officers found two powerful rifles, four handguns and other firearms and ammunition in Mr Gonzalez's vehicle along with a map marking the White House.

An unnamed federal law enforcement official told the Associated Press news agency Secret Service agents had interviewed Mr Gonzalez twice during the summer but concluded there was no evidence he was a security threat.

President Barack Obama and his family were not at the White House when the intrusion happened, having departed about 10 minutes earlier by helicopter.

The new fence went up late Monday evening.

The Secret Service, which protects the president, the vice-president, their families and visiting foreign dignitaries, in addition to other security duties, did not say how long the second barrier would be in place.

A review of security was initiated by Secret Service director Julia Pierson, who also ordered "the immediate enhancement of officer patrols and surveillance capabilities" around the White House.

Pennsylvania Avenue, which runs in front of the north facade of the White House, was closed to vehicular traffic in 1995 but remains highly popular with tourists as well as residents and office workers seeking a short cut through the parks surrounding the president's home.

Since Friday Washington DC residents and media figures have angrily rejected the suggestion the Secret Service screen pedestrians and cyclists who want to enter the closed stretch of Pennsylvania Avenue or block it off entirely.