About 25 passengers are being held hostage by foreign gunmen on a bus in the Greek capital Athens. Armed officers have surrounded the vehicle, which was hijacked just before dawn on its route from the town of Marathon into central Athens. The driver of the bus escaped. The hijackers, reportedly Russian men, asked to be driven to Athens airport and flown out of Greece. In the last few minutes, a man has left the bus with his arms raised. A police spokeswoman said the man was one of the passengers. Witnesses said at least two shots were fired shortly after police vehicles approached the bus. No-one was injured. A police official said a group of negotiators had arrived at the scene, outside a nightclub. A fleet of ambulances was also on standby close to the scene. Motive unknown The bus was seized at about 0600 (0400 GMT), shortly after the men boarded the bus in the suburb of Pikermi. Besides the driver, the ticket inspector and a passenger also managed to get away, reports said. "I stopped the bus, I opened the doors in order for the people to come out, I opened my door as well and I pulled one woman out," the driver, who was not named, told Greek television. The gunmen are said to be carrying hunting rifles or shotguns, and claimed to be armed with explosives. The pair demanded that a new driver be provided to take them and the bus to Athens airport, threatening to harm hostages if their demands were not met. Greek government officials suggested that at least one hijacker was Russian, but addressed hostages and negotiators in Greek. "Tell them to get all the police away from here. We want to go to the airport. "All passengers will get off there. We haven't harmed anyone, but if the driver is delayed I said that I will strike," the Associated Press reported him as saying. Roads nearby were cut off by police, ambulances parked near the scene, a helicopter hovered overhead and news crews were being held back. The curtains of the bus were drawn. Earlier police reports had suggested they were Albanian. Five years ago, Greece witnessed two bus hijackings within two months. In both cases, an Albanian man took control of the vehicle, demanding money and safe passage to Albania. Both hijackers were shot dead by security forces. In one of the incidents, a passenger was also killed.