The Security Service of Ukraine (SBU) announced Thursday that it has uncovered a cell of Islamic State terrorists operating in the capital city of Kyiv.

Security officials seized extremist literature, explosives, grenade launchers, foreign funds, and evidence of financial transactions with ISIS leadership in Syria when raiding the homes of the suspects.

Ukraine’s UNIAN Information Agency reported the leader of the Kyiv cell is “wanted by one of the Eastern European countries for participating in Syria hostilities.” He reportedly used forged documents to enter Ukraine, then forged more Ukrainian and Russian passports to bring in “like-minded” foreign nationals from the Middle East and Central Asia.

“According to the investigation, some of them are active ISIS militants,” the SBU stated. Documents uncovered in the raid indicated the cell intended to “lay low” in Ukraine after conducting its planned terrorist attacks, although some members also evidently discussed returning to Syria to participate in further Islamic State operations there.

The SBU raided a total of nine residences in and near Kyiv, recovering both bomb-making materials and assembled explosive devices.

Ukraine has been viewed as a potential “safe haven” by Eastern European ISIS recruits, in part because they believed Ukraine would be easy to enter with fake documents, hard to get extradited from, and lax in pursuing Islamist terrorist threats because the attention of Ukrainian authorities is focused elsewhere. Eastern European militants captured in Turkey and Syria often specified Ukraine as the country to which they preferred deportation.

A high-ranking Islamic State official, a Georgian national named Cezar Tokhosashvili who styled himself as “Al Bar Shishani” after joining ISIS, was arrested by the SBU in November 2019 in a joint operation with American and Georgian intelligence agencies. U.S. officials referred to Tokhosashvili as the Islamic State’s “minister of war.” Like the unnamed ISIS cell leader arrested on Thursday, he entered Ukraine with a false passport and was living in a home near Kyiv at the time of his arrest.

Thursday’s announcement by the SBU is significant because until now, ISIS militants generally seemed to regard Ukraine as a place to regroup, recover, and plan their next moves, rather than planning to target Ukraine itself with terrorist attacks.