Greek authorities on Wednesday vowed to capture the "terrorist" gunmen who wounded six officers outside an Athens police station by firing nearly 100 rounds in a drive-by attack.

No group has claimed responsibility for Tuesday night's shooting, but police suspect resurgent far-left militants who have escalated attacks after the fatal police shooting of a teenager in Athens in December.

Michalis Chrissochoidis, a minister in charge of police, said it was "pure luck" that nobody was killed in the attack in the northern suburb of Aghia Paraskevi.

Two officers — including a trainee policewoman — remained in intensive care Wednesday, but their lives were not in danger, hospital officials said. The other four suffered lighter gunshot wounds.

Police found 99 bullet casings from Kalashnikov assault rifles outside the Aghia Paraskevi precinct, which came under fire by at least two gunmen on a motorcycle as officers were changing shift.

Another four people may have been involved in the attack, on the eve of a national holiday commemorating Greece's World War II resistance to invading Axis troops.

Attica police chief Ioannis Rahovitsas said tests showed the rifles had not been used before in Greece.

"To fire 100 bullets with at least two automatic weapons at six people means you are determined to kill," Chrissochoidis said. "This is an escalation. ... Our duty is to arrest the culprits and hand them over to justice." He called the attack "100 percent terrorism."

Police forensics experts are examining three stolen motorcycles thought to have been used in the attack, which were found abandoned close to a nearby subway station.

Greece's new Socialist government has promised to crack down on anarchist and far-left groups that have stepped up bombings and shootings after the teenage boy's death last year, which sparked days of rioting in major Greek cities.

"There is no place for ideological obsession and stereotypes when young people are attacked ... be they schoolchildren or trainee police officers," Chrissochoidis said.

Authorities had believed that years of far-left terrorist violence had come to an end after the arrest of several members of the country's deadliest group, November 17, in 2002 — when Chrissochoidis was also in charge of police.

But in 2007, a group called Revolutionary Struggle fired a small anti-tank rocket at the U.S. Embassy in Athens, causing minor damage and no injuries. The same group shot at riot policemen in central Athens in January, severely injuring one officer

In June, gunmen killed an anti-terrorist policeman guarding a witness in central Athens. A group called Sect of Revolutionaries said it carried out the attack to avenge the teenage boy's death.

Police are bracing for potential violent protests on the Dec. 6 anniversary of the 15-year-old's killing, for which two officers will stand trial on Dec. 15.