* MP from leftist anti-bailout Syriza party says attacked
* Far-right Golden Dawn party denies involvement
* Politicians from across spectrum condemn assault
* Press says everyday violence getting out of hand
ATHENS, Dec 17 (Reuters) - Greece's government on Monday condemned an attack against a leftist lawmaker which has raised fears that far-right violence in the crisis-hit nation is spiralling out of control as "unacceptable".
Dimitris Stratoulis, an MP from the leftist Syriza party, said three men in their 30s had kicked and punched him in the head during half-time at a soccer game on Sunday evening.
The men had identified themselves as members of the far-right Golden Dawn party and had told him "We are going to kill you now", he said. The party denied involvement in the attack.
Syriza, the anti-bailout party which is leading in opinion polls, demanded the immediate arrest of the perpetrators, saying tolerating Golden Dawn would lead to the loss of lives.
Lawmakers from across the political spectrum spoke out against the attack.
"We harshly condemn the attack," Simos Kedikoglou, a Greek government spokesman, said in a statement. "Any kind of attack and threat is unacceptable in our democracy. Violence has no place in our culture."
Golden Dawn, which has been linked to violent assaults against immigrants, has surged in popularity as Greece's economic crisis has deepened. It emerged from obscurity to enter parliament this year for the first time.
"Golden Dawn has nothing to do with the attack against the Syriza MP," the party, which would be the third-largest in Greece if elections were held now, said in a statement.
"The left-wing politicians who foment violence ... should stop using the name of Golden Dawn."
In a front-page editorial, influential daily Ta Nea called on the government to do more to curb rising violence amid the crisis.
"Condemning the attack ... is not enough. Uncontrollable violence is becoming part of everyday life in Greece. Dealing with Golden Dawn is a crucial issue," it wrote.
The Efimerida Ton Syntakton newspaper said the attack had revealed Golden Dawn's true colours and that Greeks had to now evaluate how much violence they were willing to tolerate.
In June, Golden Dawn's spokesman Ilias Kasidiaris slapped a female leftist politician in the face and threw a glass of water at another during a live TV debate, causing a political uproar and an order for his arrest.
Speaking to Greek TV outside the stadium late on Sunday, Stratoulis, who showed no visible signs of injuries, said he had filed a complaint with the police and could identify his attackers. The assault was "a cowardly, fascist, gang attack", he said. (Reporting by Karolina Tagaris; Editing by Andrew Osborn)