A Turkish interior ministry official on Thursday said 37 people were detained in Turkey and 16 more were held in police raids in Italy, Germany, Belgium and the Netherlands, targeting Turkey's Revolutionary People's Liberation Party-Front (DHKP-C).
Greece has also arrested another man suspected of links with the organisation.
Security forces in the Philippines also arrested four Turkish nationals suspected of having ties with international "terror groups," but a military spokesman said there was no link with the European crackdown.
The DHKP-C is against the United States, NATO and the Turkish establishment and has said it was responsible for bomb attacks in Turkey.
Prosecutors in the central Italian city of Perugia said they coordinated an early morning, pan-European operation against the organization after an 18-month investigation. Five people were arrested in Italy – two Turks and three Italians - and further arrest warrants were issued for suspects living elsewhere.
"As far as we know there are no connections with Islamic terrorism, but this is only the beginning of the investigation and we have a lot to learn," prosecutor Nicola Miriano said.
Dutch authorities said police mounted five separate raids in Amsterdam and the southern towns of Ettenleur and Maassluis and seized material such as computers and mobile phones on suspicion that some people were running communications for an armed group.
Greek police said they separately arrested a German citizen of Kurdish origin on suspicion of links to the same group.
They said the 30-year-old Sinan Buzkurt was wanted in Germany, which had issued an international warrant for his arrest.