TAIPEI (AFP) - Taiwan stepped up security measures after a driver rammed a huge truck through a bullet-proof screen and into the main gate of the presidential office, apparently intentionally.

A man identified only by his family name Chang drove the 35-tonne truck through railings, the screen, and up a set of steps before coming stuck in the gate leading to the office's main building, police said.

President Ma Ying-jeou was not in at the time as he is on a state visit to Sao Tome and Principe in Africa. He has been notified of the incident, his spokesman said. She added that security measures had been beefed up at the Taipei site following the early morning incident, and that police were investigating a cause and motive. She did not specify what the increased security measures were.

The impact from the crash knocked the driver unconscious, and he was taken to a nearby hospital for treatment, police said. No one else was injured and the truck was towed from the scene.

"Chang has a criminal record, and so far he has refused to answer any questions," police spokesman Fang Yang-ning said, adding that they suspect he crashed "intentionally".