PATRAS, Greece (AFP) - Two men have been arrested in Greece after foremen for strawberry growers allegedly shot and wounded 27 migrant labourers demanding long-overdue pay, police said on Thursday.

The migrants, mainly from Bangladesh, were hospitalised in the western port of Patras and other areas with gunshot wounds after allegedly being fired upon late on Wednesday by three foremen for the growers in the village of Manolada, one of the main areas of strawberry production in Greece, local police said.

A 57-year-old landowner was arrested as a "moral instigator" of the alleged shootings, as was another man for sheltering two of the presumed perpetrators overnight, police said.

The migrants had been working in local fields, some without being paid for the past six months, the police said. Around 200 of them went to demand their money on Wednesday when they were fired upon.

The government condemned the attack and anti-racist groups were planning a demonstration in the area later in the day.

Government spokesman Simos Kedikoglou said the attack was "inhuman" and "outside Greek morality" and pledged an immediate response by the authorities.

But the Communist-affiliated PAME union noted that the incident was only the latest in a long history of abuse of migrant workers in Greece.

PAME said the workers had been fired upon with shotguns and pistols. It claimed 33 were hurt, while the police said 27 were wounded, one of them critically.

"Growers and landowners have operated with cover from the government and justice for years, creating a hell-hole with slavery labour conditions," the union said.

"Modern slaves in Manolada work in stifling conditions, pay rent to their exploiters and are lodged in sheds without water and electricity, piled upon each other," it said.

Ms Natassa Panagiotara, head of the labour centre in the neighbouring town of Amaliada, spoke of "19th century-style plantations" operating in this manner for over a decade.

"The Greek state knows what is going on...but there are only two labour inspectors in the area," she told Skai radio.

A local labourer who also spoke to the station said workers had been promised 22 euros (S$36) for seven-hour shifts.

He said workers "bathed in a barrel and drank from a water hose" and were afraid of "being killed or having their hut set on fire" if they pressed their claims for pay.

Calls for a boycott on Manolada strawberries rapidly spread online, but Ms Panagiotara warned against indiscriminate action.

"There are family growers in the area who run their own farms without migrant labour and are just as hungry as other Greeks," she said.

In 2008, Manolada was the focal point of a rare strike by hundreds of migrant workers against near-slavery conditions in the fields.

The treatment of migrants in Greece has long been criticised by domestic and international rights groups, to little avail.