The Greek government, political parties and society strongly condemned on Thursday a shooting incident during a back pay dispute in Peloponnese peninsula in western Greece, which injured 28 migrant farm workers on Wednesday evening.

The incident occurred when some 200 strawberry pickers - in the wide majority Bangladeshi nationals - requested overdue wages of six months, according to police.

During a heated argument, one of the three Greek supervisors fired at the workers with a shotgun and seriously wounding eight persons and slightly injured 20 more, hospital sources was quoted as saying.

As police are searching for the supervisors and have detained the owner of the field at the outskirts of the town of Manolada, the incident has caused outcry in Greece.

"This inhumane attack by gunmen is condemned in the most absolute manner by the entire Greek society. This unprecedented, heinous act is alien to Greek peoples' morals," Greek government spokesman Simos Kedikoglou said.

Political parties participating in the ruling coalition and of the opposition issued similar statements against "this criminal, racist act."

Labor unions and human rights groups called on authorities to attribute justice, noting that it is not the first violent incident against migrant workers in the same region.

Over the past five years there have been at least two cases of abuse against workers in back pay arguments. In 2008 hundreds of strawberry pickers held a week-long protest over back pay and working conditions.

According to estimates by local officials, there are some 4,000 foreign nationals - several undocumented - working in the region's fields.

Despite the severe debt crisis which has hit Greece hard since 2010, fuelling jobless rates, several fieldworkers are still low paid migrants.

Foreign workers have been targeted by far-right extremist groups at an increasingly rate since the right-wing Golden Dawn party entered the Greek parliament for the first time last spring.

The party is capitalizing on Greeks' frustration at the harsh austerity introduced to tackle the debt crisis and currently ranks third in opinion polls.

The attack at Manolada occurred as an expert of the United Nations Human Rights Council is due in Athens next week to inspect the impact of the crisis on human rights.