Greece must not relax a fiscal effort that is starting to bear fruit after painful sacrifices, IMF chief Christine Lagarde said on Tuesday as Athens lined up for another creditor audit.

"Now is not the time to relax the effort," Lagarde told state television NET in an interview recorded last week.

Greece's central bank governor says the country's four largest lenders will be given until the end of May to complete a major recapitalization program.

Bank of Greece governor George Provopoulos told state-run NET television late Monday that the banks — National, Eurobank, Alpha, and Piraeus — would be given an extension of up to a month for the program backed by bailout funds.

A major thunderstorm on Friday flooded roads and homes in Athens, causing massive gridlock across the Greek capital and knocking out parts of its metro network, authorities said.

The fire department said it had received some 700 calls to drain water from houses and businesses as ankle-high water filled the city's streets.

Qatar has rejoined a public competition to develop the former Athens airport, one of the prized sites of Greece's privatization drive, a Greek spokesman said on Wednesday.

The emirate "has signed the confidentiality agreement and is returning to the Hellinikon tender," government spokesman Simos Kedikoglou told To Vima radio.

Greek authorities on Sunday condemned a bomb blast at an Athens shopping mall that left two security guards lightly injured.

In the latest in a series of violent attacks, an explosive device went off at 10:40 am (0840 GMT) on the first floor of the multi-story Athens Mall, in a northern suburb of the Greek capital, where shops as well as a branch of the National Bank of Greece are located.

Hundreds of people held a rally against racism and fascism in central Athens on Saturday as mourners gathered to pray over the body of a man killed in a suspected racist attack.

Nearly 3,000 people, according to state broadcaster NET, joined the peaceful protest organized amid a nationwide surge in xenophobic sentiment.

Hundreds turned out in Athens on Saturday to protest against racism and a surge in neo-Nazi activities in Greece and other European countries, in a demonstration backed by prominent European figures and human rights activists.

Police said about 500 people rallied in Athens' central Syntagma Square opposite the Greek parliament, alongside a large banner reading "Europe against neo-Nazis". Organizers put the number at nearly 1,000.

A bomb exploded early on Tuesday outside an office of a Greek neo-Nazi group blamed for violent attacks on migrants, causing material damage but no injuries, a police source said.

The 02:00 GMT explosion blew holes in the wall of the Golden Dawn office in the industrial district of Aspropyrgos west of Athens, and smashed windows at neighboring buildings, the police source told Agence France Presse.

A theatre in Athens on Thursday said it would end performances of an American play portraying Jesus Christ as homosexual that sparked violent protests by neo-Nazi groups.

"Corpus Christi performances are ending," the play's translator and its director said in a joint statement.

The 'troika' of international creditors called time out Friday on lengthy bailout negotiations with the Greek government, pending further consultations.

"The discussions since the beginning of September have been very intense," Simon O'Connor, spokesman for EU Economic Affairs Commissioner Olli Rehn told a regular news conference, saying negotiators were "leaving this weekend" and "returning in about a week.