ATHENS -- A bomb device exploded outside a Greek Orthodox Christian church in the center of Athens on early Thursday, injuring two persons, Greek national news agency AMNA reported.

The two slightly injured are a church employee who found a suspicious package and alerted the police, and a police officer who rushed to the site.

No warning telephone call was made before the explosion and no group has claimed responsibility for the attack.

Greek anarchist and terrorist groups who have been operating in the country for decades targeting politicians, police, media and financial targets, usually make warning calls to media outlets to avoid casualties.

This was the case on December 17 this year when a bomb blast caused extensive material damages, but no injuries at the headquarters of local media group SKAI.

About 15 minutes after the explosion which happened at 7:15 a.m. local time, there was a scheduled mass, while next to the church is a popular cafe.

"It was a loud explosion, but not very strong," Andreas K., a local, told Xinhua.

"I heard a deafening sound while I was at home and then sirens of an ambulance and police vehicles... I went outside on the balcony to see what is happening," Evangelia T., a neighbor, added.

Attacks on religious buildings (in the overwhelming majority on Greek Orthodox churches) by so-called anti-establishment groups in many cases, are on the rise in recent years, according to a recent report on local "Eleftheros Typos" (Free Press) daily which cited the Education, Research and Religious Affairs Ministry data.

In 2017 a total of 556 incidents of vandalisms, burglaries etc. were recorded against places of worship, including 537 against Orthodox Christian churches and cemeteries.

A year ago according to the ministry's figures, a total of 215 such attacks on Christian churches, synagogues and other religious sites were recorded.

Located in the district of Kolonaki, 500 meters from the Greek parliament, the targeted church was inaugurated in 1931, while famous Greek architects, painters, sculptors and other artists contributed in the construction and decoration.

On early afternoon Thursday, bomb disposal experts also rushed to the headquarters of the ruling Radical Left SYRIZA party in central Athens for a suspicious package which turned out to be a power bank.