* Shooting follows spate of attacks on public figures
* Bullet shot through window of Athens HQ but no one hurt
* PM Samaras says "you cannot shoot democracy"
By Dina Kyriakidou and George Georgiopoulos
ATHENS, Jan 14 (Reuters) - Unidentified attackers opened fire on the Athens headquarters of Greece's governing New Democracy party with a Kalashnikov assault rifle early on Monday, in what the government said was a worrying escalation in political violence.
Police said a bullet pierced the window of the office that conservative Prime Minister Antonis Samaras maintains in the building near the city centre, but no one was hurt.
The early morning gun assault follows a spate of makeshift bomb attacks against journalists and political figures in the past week, some claimed by leftist groups angry at Greece's deep financial crisis.
Greece is in the sixth year of a recession that has fuelled anger against foreign lenders and the political class, blamed by Greeks for bringing the country close to bankruptcy.
Addressing supporters outside his party office on Syngrou Avenue late on Monday, Samaras condemned the shooting.
"You can shoot a person or at building, as they did, but you cannot shoot democracy," he said. "Let them hear it then, those who must: Democracy will not be terrorised."
Political violence is not uncommon in Greece but deadly attacks are rare.
Officials said Samaras no longer uses his office on Syngrou Avenue and was not present at the time of the shooting.
"At about 3 a.m. (0100 GMT), guards saw two men coming out of a black car and firing with a Kalashnikov at the building, which was empty at the time," said a police official speaking on condition of anonymity.
He said at least nine bullet casings were recovered from the scene and police were examining a burnt-out car found a few kilometres (miles) away. Anti-terrorism police cordoned off the area and were checking security cameras near the party building.
Government spokesman Simos Kedikoglou said even a symbolic attack on the prime minister was unheard of.
"This is a new, worrying escalation of the effort to create terror in our society," he said.
SPATE OF ATTACKS
The recent attacks have targeted public figures. On Sunday, the Athens home of Kedikoglou's brother was hit by a petrol bomb and three New Democracy offices in the city were targeted on Friday. No injuries were reported in the attacks.
Police blamed Sunday's attack on far-left protesters angry at a police raid last week that cleared a squat popular with anti-establishment groups. About 100 people were arrested.
On Friday, a number of small homemade bombs exploded outside the Athens homes of five Greek journalists working for major media outlets. In an Internet statement, a group going by the name 'Lovers of Lawlessness' claimed responsibility, accusing the journalists of doing the bidding of politicians.
The conservative-led coalition government has imposed harsh tax hikes and salary cuts in its six months in power to secure vital international cash for Greece, where unemployment has reached about 27 percent and living standards have plunged.
The government says Syriza, the radical leftist main opposition party, tacitly backs anti-establishment groups and their attacks. Party spokesman Panos Skourletis denied that.
"This is certainly a dangerous escalation of terrorist attacks of blind violence, which are completely condemned by Syriza," Skourletis said of Monday's attack.