The first special detention centre for illegal migrants due to be deported opened at the outskirts of Athens Sunday, a week before the May 6 general elections, as the issue has turned into a key topic on the agenda.

The first 56 detainees were transferred at the Amygdaleza former police training centre, which has been renovated in recent weeks to house up to 1,000 persons, despite reservations by local society and opposition political parties.

The outgoing administration of Lucas Papademos launched this spring a two-year plan to combat the chronic problem that adds financial and social strain to the debt-laden country, in particular as it struggles amidst deep recession and record high unemployment rates over the past two years to avoid a disorderly default.

Some 130,000 people illegally enter Greece on an annual basis, according to official data, as the country has become a main transit point of illegal migrants, mainly from Asia and Africa, dreaming of a better future in western European countries in recent years.

The plan foresees the creation of about 30 such reception centres for unregistered migrants nationwide over the next months, as Athens faces the risk of a potential exclusion from the European Schengen common travel zone over the issue, unless it swiftly safeguards its borders effectively.

Inaction is no longer a choice, stressed in many occasions recently Michalis Chryssohoidis, the socialist minister in charge of public order in the interim six-month coalition with the conservatives.

But the scheme has triggered concern over the detention conditions of the immigrants and its efficiency.

Calling for a comprehensive political asylum and immigration national strategy, critics argue that it is a pre-election publicity ploy that will not address the matter substantially. Tens of thousands undocumented migrants will remain in city centres living in dire conditions, fuelling petty crime and racism.

It is estimated that at the moment about one million migrants live in Greece, which accounts to some 10 percent of the country's population. Approximately one in two immigrants is undocumented.

Local political analysts link the rising popularity of far-right group "Chryssi Avgi" (Golden Dawn) in recent months with the illegal migration issue. For first time in its history the party is expected to enter the parliament at the upcoming elections, according to the opinion polls.

Centre-right New Democracy (ND) party leader Antonis Samaras, who is frontrunner in the polls, according to pollsters, has said that he will implement a tough immigration policy.

ND will repeal a law that allows second-generation immigrants whose parents live in Greece legally, to apply for Greek citizenship, he has said.

The conservatives argue that the law that was introduced two years ago has deteriorated the situation, giving the undocumented immigrants the impression that they can secure legal status in an EU member country.