The blast broke several windows in the court facade and at nearby buildings
A bomb exploded early Friday outside one of Greece's main courthouses, officials said, but police had cleared the area and nobody was hurt.
The explosion occurred at 0125 GMT outside the Athens appeals court after calls warning of a bomb had been made to the media, police said.
The blast broke several windows in the court facade and at nearby buildings.
The bomb was inside a backpack left at the building entrance by two men who fled in a small van, a police source told AFP.
It had earlier been reported that a motorbike was used.
The police source said that the assailants had also fired at the guard to stop him from pursuing.
Police later found a torched van a few blocks from the scene. A bullet casing has also been recovered from near the courthouse.
There was no immediate claim of responsibility.
Police suspect a far-left group calling itself Popular Fighters Squad, which has carried out shooting attacks against the Israeli embassy in 2014 and the German ambassador's residence in 2013. In 2015, they exploded a bomb outside the Greek Federation of Enterprises, the country's top industrial lobby.
The incident occurred amid a bitter row over foreclosures of properties over longstanding debts to Greek banks.
The government has tabled new legislation, hardening rules against anti-foreclosure protesters.
Foreclosures are now increasingly being held online after successive protests blocked property auctions, prompting Greek notaries to repeatedly go on strike to protest a lack of state protection.
Greek banks are burdened by around 100 billion euros ($119 billion) in non-performing loan exposures -- about half of overall lending -- and the issue has repeatedly been highlighted by the European Central Bank.
The notaries insist that family homes are protected under a 2010 law that is annually renewed, and that the anti-foreclosure protests have mainly aided wealthy debtors playing the system to their advantage.