Police fire tear gas at Greek farmers rallying against the latest bailout in Athens

REUTERS/Alkis Konstantinidis

ATHENS (Reuters) - Greek riot police fired tear gas at farmers protesting against pension reform plans on Friday who hurled stones at the agriculture ministry in central Athens ahead of a major demonstration outside parliament scheduled for later in the day.

Under the planned reform of the pension system demanded by Greece's international lenders, farmers face a tripling of their social security contributions and higher income tax. They have been blockading motorways across Greece for over three weeks.

Greece's left-leaning government says the step is necessary to ensure future pensions for the group, whose benefits have so far been almost completely subsidized by the state.

About 800 farmers from the island of Crete arrived in Athens early on Friday and rallied outside the agriculture ministry waving Greek flags and chanting: "They won't make us bend."

Riot police guarding the entrance to the ministry fired teargas to disperse farmers who hurled tomatoes and stones at the building smashing windows and used shepherd's crooks to repel police during the tense but brief scuffles.

More farmers were heading to the capital to join the main rally, which was scheduled for the evening and was expected to test Prime Minister Alexis Tsipras's resolve to push through unpopular reforms.

Some of the farmers started setting up tents on Syntagma Square, the scene of many violent clashes during anti-austerity protests over the past few years.

Police said they would not allow farmers with tractors to drive into Athens.

The pension reform is a key term of Greece's bailout review, but has triggered anger among professional groups including lawyers, teachers, doctors and actors.

Tsipras, who was elected last year promising to end austerity but was then forced to accept a third bailout in July, is feeling the pressure as he struggles to conclude a bailout review with lenders and also convince angry Greeks that their sacrifices will pay off. He has a tiny parliamentary majority.

Earlier this week, Tsipras said he was willing to hold talks with the farmers on possibly amending the pension reform bill to lessen the pain, but they rebuffed his overtures.

(Reporting by Lefteris Papadimas and Alkis Konstantinidis; Additional reporting Lefteris Karagiannopoulos; Editing by Gareth Jones)