ATHENS (Reuters) - Three self-proclaimed Greek anarchists were sentenced to jail on Wednesday for involvement in a seven-year campaign of attacks and attempted murders, including a rocket propelled grenade assault on the U.S. embassy in Athens.

The three had admitted being members of Revolutionary Struggle - a group which declared war on all forms of government in 2003 and later said it was also protesting against austerity measures brought in to cope with Greece's financial crisis.

They were the first convictions linked to the violence, which also included the 2009 bombing of the Athens stock exchange.

The three were each sentenced to 25 years in prison, two of them in absentia. Well-known anarchist Nikos Maziotis and his partner Panagiota Roupa went on the run last year during the legal proceedings.

The three had refused to make any comment in court about whether they were involved in the attacks.

Revolutionary Struggle has claimed responsibility for 16 attacks since 2003. It shot and wounded a policeman in 2009 in revenge after an officer shot dead a teenager, sparking the country's worst riots in decades.

No one was wounded when the grenade hit the U.S. embassy in 2007, or in the attack on the stock exchange, which smashed windows and coated the front of the building in soot.

The three were not convicted of being physically present at any of the attacks.

Greece has a long history of political violence - Revolutionary Struggle emerged a year after Greece's deadliest guerrilla group November 17 was dismantled.

Small-scale attacks have increased since the financial crisis broke out fuelling public anger against banks, foreign lenders and politicians.

In January, a small bomb exploded at an Athens shopping mall, slightly wounding a guard.

Last month, a bomb went off outside the home of a prominent Greek ship owner.

Another two people were jailed for seven years on Wednesday for being members of the banned Revolutionary Struggle group and another three were acquitted on that charge. All of those five had denied being members.

Most of the defendants were arrested in 2010, when the authorities said they had broken up the group.

(Reporting by Renee Maltezou; Editing by Andrew Heavens)