An explosive device went off outside Greece's labour ministry in central Athens early on Saturday but caused no injuries, Greek police said.
A Greek newspaper received a phone call from an unknown caller that a bomb had been planted at the ministry and had informed the police, who cordoned off the area before the explosion, which caused damage to the building and broken windows, police said.
The caller said a previously unknown guerrilla group was behind the attack, a police official said on condition of anonymity.
Police have launched an investigation into the incident.
Greece has a history of political violence. Small bomb and arson attacks are frequent, and most of them do not cause serious damage.
However, the government said it was worried by the incident.
"The attack is very serious and has to do with a serious crime," government spokesman Pavlos Marinakis told Open TV broadcaster on Saturday.
The US and Iran failed to reach an agreement to end their war despite marathon talks that concluded on Sunday in the Pakistani capital Islamabad, jeopardising a fragile ceasefire.
At least 30 people were killed on Saturday in a stampede at the Laferriere Citadel in the northern countryside of Haiti, authorities said, warning that the death toll could rise.
A cyclone battered New Zealand's North Island on Sunday, cutting power to thousands of residents and forcing hundreds to evacuate, as officials warned conditions would worsen through the day.
Negotiations between the United States and Iran appeared to have concluded for now, Iran's government has announced early on Sunday, after a series of talks in Pakistan to end the six-week war between Washington and Tehran.
Costa Rica on Saturday has received the first group of migrants from other countries deported from the United States under an agreement signed in March between the two countries, local authorities said.
Sheikh Abdullah Bin Zayed Al Nahyan, Deputy Prime Minister and Minister of Foreign Affairs, has strongly condemned the terrorist plots that sought to undermine security, incite chaos, and carry out acts of sabotage in Kuwait.
Dubai's Knowledge and Human Development Authority (KHDA) has introduced two options to allow private Early Childhood Centres to offer home-based learning for children below the age of six when government-mandated distance-learning is in place.
Dubai’s Roads and Transport Authority (RTA) has installed 726 public bus shelters across key areas to the Emirate to serve more than 192 million riders annually.