About 1,300 farmers who had arrived in Athens from the island of Crete overnight headed to the agriculture ministry, which was sealed off by police buses.
Tempers flared after reports spread among the assembled crowd that officials had refused to see a delegation from the farmers, witnesses said.
A number of farmers, some holding shepherd's staffs, charged the building and smashed windows of two parked police buses, with police responding by using tear gas, dispersing demonstrators into side streets.
Riot police remained at the scene, with some demonstrators occasionally appearing to hurl stones at them.
Violence erupts as Greek farmers clash with police in Athens Mon, March 6, 2017
Greek farmers clashed with police in central Athens on Wednesday when a protest against tax and pension reforms mandated by the country's multi-billion-euro bailout turned violent
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A farmer from the island of Crete stands next to riot police during clashes outside the Agriculture Ministry in Athens
One demonstrator punched a hole in a police bus window, placing a large blue-and-white Greek flag in it. Shops in the area, a commercial district in downtown Athens, were shuttered.
Farmers have been engaged in a long-running feud with Greek authorities over social security laws introduced in mid-2016 which force them to pay on imputed earnings upfront, and higher pension contributions.
Greek farmers clash with police in protest against tax and pensions reforms
Farmers who arrived overnight from Crete for the agriculture ministry which was sealed off by police
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Farmers used shepherd's staffs to charge police who responded with tear gas
Greece is now engaged in discussions with creditors on additional economic reforms required to meet bailout obligations.
The crisis-hit country signed up to a new credit lifeline worth €86 billion in mid-2015, its third since 2010.
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