ATHENS - A small makeshift bomb exploded outside a branch of Greece's second largest lender, Eurobank , in central Athens early on Saturday, causing no injuries or serious damage, a police official said.

The device consisted of two gas canisters but only one of them blew up, blackening the shutters of the branch, the official said.

There have been several low-level attacks on businesses and politicians in Greece since the cash-strapped nation adopted tough austerity measures under the terms of two successive bailouts by the EU and the IMF.

The attack is the third in the last two weeks. A small bomb exploded outside a branch of the reform ministry on Monday, and a similar device caused minor damage outside the office of former socialist Prime Minister Costas Simitis earlier this month.

Greece is officially in a pre-election period after calling early elections for May 6. But most polls show that the election will fail to provide a clear result and that the two biggest parties, the conservative New Democracy and the Socialist PASOK, may face difficulties in renewing their coalition government.