ATHENS, Jan. 5 (Xinhua) -- Unknown gunmen shot and seriously wounded a 21-year-old police officer in Athens with a Kalashnikov assault rifle early Monday morning, police said.

    The policeman was in critical but stable conditions after a surgery in the nearby Red Cross hospital for injures in the chest and thigh, according to the Health Minister Dimitris Avramopoulos.

    The police squad on guard near a culture ministry building in the Exarhia district of Athens was attacked early Monday morning by unknown gunmen who had already escaped. So far no one has claimed the responsibility for the shooting, police said.

    Greece's anti-terror squad has launched the investigation. It is the second such attack since the Greek police shot dead a teenager last month which prompted Greece's worst riots in decades.

    Last month shots were fired at an anti-riot van in Athens, missing the 23 police on board. The shots came from two Kalashnikov assault rifles fired from inside a park that houses the Athens university campus.

    More than 15 cartridges have been collected at the site in the Exarchia district and then taken to a lab to identify whether they came from the same weapons which fired against the police last month.

    The entire Exarchia district was closed off immediately after the attack. Police have taken in more than 40 individuals for questioning.

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