A group self-styled anarchists attacked four banks in an Athens suburb and a local branch of the ruling New Democracy party, police said.
About 25-30 protesters smashed windows and automatic teller machines at around 1:25 am (2225 GMT).
A few hours earlier another New Democracy office had been firebombed, also at an Athens suburb, police said. No one was arrested.
Attacks by anarchists have increased dramatically since the shooting of a teenager by a police officer on Dec 6, 2008. Most of the attacks occur late at night, but banks and shops have also been attacked during daytime, leading the government to promise increased police presence.
In February, anarchists tried to blow up a Citibank branch with a powerful bomb that failed to explode.
A posting at a Web site widely used by anarchists and extreme leftists vowed to continue their attacks on the "rotten world of consumerism using expropriation, looting, sabotage and destruction".