HILDESHEIM, Germany (Reuters) - An armed man hijacked a city bus on Friday and forced the driver on a 105-mile chase across northern Germany with passengers aboard before surrendering to police.

None of the nine hostages still on the bus at the end of the seven-hour standoff was injured, police said. Eyewitnesses told Germany's N24 television network that no shots were fired at the end of the hijacking.

"The hostage-taker has surrendered," a police spokeswoman said. She did not have any further details.

Officers surrounded the bus when it stopped on the A7 motorway near Hildesheim in central Germany after being pursued by police cars and ambulances. It remained idle for the last few hours of the stand-off.

The drama started in the northern town of Bremen when the man boarded the bus at about 9.40 a.m. (3:40 a.m. EDT) and threatened the driver with a gun. He took about 15 passengers hostage but released several at various points during the bizarre journey

Police said they believed the gunman was aged between 20 and 25 and was a foreigner. Several children were on the bus.

One of the hostages released from the red and white Bremen city bus earlier had been complaining of heart trouble.

Police said the hijacker had fired into the air once during the pursuit and had demanded to speak to the mayor of Bremen but his motive remained a mystery.

The A7 motorway, one of Germany's main north-south arteries, was blocked off, causing long tailbacks in busy Friday afternoon traffic.

Police said the man had demanded food and a second bus driver to continue his journey south.

Television pictures showed the bus closely surrounded by unmarked police vehicles.

It was Germany's second such hijacking in two weeks after police stormed a bus seized by an armed bank robber in Berlin on April 11, shot him in the shoulder and rescued his two hostages unharmed.

Friday's hijacking was a grim reminder of an incident which shocked Germany in 1988 when bank robbers killed two female hostages they had seized in the town of Gladbeck after holding them captive during a two-day motorway chase with police.

The police spokesman said the hijacker was of "southern appearance" -- a loose description German police often use for people from southern Mediterranean, Arab or Asian countries.