ATHENS — Police in Greece said Friday they have seized grenade launchers and other weapons in raids against suspected members of a far-left Turkish armed group.

The raids were carried out at two properties in Athens Thursday against alleged members of Revolutionary People’s Liberation Party-Front, or DHKP-C, a group that is considered a terrorist organization by Turkey, the United States, and the European Union.

Eleven people were arrested in the operation that involved the anti-terrorism division of the police and the National Intelligence Service, authorities said. They were charged Friday with terrorism-linked offenses. Their lawyers said the suspects denied the charges

At one raided site, police said they found a makeshift underground storage room and tunnel, spanning a total length of 47 meters (154 feet) that ended in an adjoining vacant lot.

The weapons seized include two anti-tank launchers, two grenade launchers, four handguns and an automatic rifle. Computer and external hard drives and cellphones were also seized. It was unclear how the suspects had been allegedly planning to use the weapons.

DHKP-C is believed to have been present in Greece for years.

Last year, a Greek court cleared of terrorism and criminal arms charges nine people arrested in Athens ahead of a 2017 visit by Turkey’s president and accused of belonging to the group.

In 2014, four Turkish men were arrested in Athens on terrorism-related offences in connection with DHKP-C, after a raid on an apartment that uncovered weapons, explosives and detonators. The operation followed the arrests of five Turks and three Greeks over a speedboat carrying arms that was intercepted in the Aegean Sea.

Originally founded in the late 1970s as Dev Sol, the Marxist-Leninist DHKP-C is believed responsible for a string of assassinations and bombings in Turkey, including a 2013 suicide bomb attack on the U.S. Embassy in Ankara.