Foremen at a strawberry farm in Greece opened fire on a group of migrant workers protesting against unpaid salaries, injuring 29.

Some 200 Bangladeshi strawberry pickers had gathered to protest over six-month unpaid wages at a farm in Nea Manolada, in the Ilia region of the Peloponnese, south-western Greece.

A confrontation with three foremen erupted and at least one of the farm supervisors opened fire with a shotgun.

Many workers were taken to a local hospital, none in critical conditions. Seven are still receiving treatment.

According to Police Capt. Haralambos Sfetsos, protesters "moved threateningly" towards the guards, who opened fire before fleeing the scene.

"We have identified the three foremen and are looking for them. They are three Greek men, who live locally," Sfetsos said.

Greek government condemned the "unprecedented and devastating" attack and pledged "swift and exemplary" action against the perpetrators.

The owner of the farm, who was not at the place of the shooting at the time, has been taken into custody for questioning.

A local man accused of helping the fugitives go into hiding has also been arrested.

A rally in support of the victims was held in Athens.

Famous for its strawberries Nea Manolada has witnessed other episodes of violence against immigrants in the past.

Last year, two men were arrested for beating a 30-year-old Egyptian.

In 2008 migrants workers staged a four-day strike against inhumane working and living conditions.

An international campaign to boycott strawberries from the region has been launched on social media under the #bloodstrawberries.

Tension towards migrant workers has been growing in Greece since the burst of the economic crisis.

Earlier this week, a European human rights watchdog warned against the "upsurge of hate crime" in the country.

A report by the Council of Europe said that the "steep increase in hate crimes in Greece, primarily targeting migrants, is an issue of grave concern," and urged authorities to take prompt action.

The report blamed a number of the attacks on the Neo-Nazi party Golden Dawn and suggested Greece could ban the party.

A campaign to boycott Manolada strawberries has been launched on social media (Twitter)