He added that intelligence gathered by the group “indicates serious preparations by (IS) cells.”
Siamand Ali, a spokesman for the Kurdish-led Syrian Democratic Forces, told The Associated Press that a group of five people believed to be part of an IS sleeper cell, two of them wearing explosive belts, had attacked checkpoints and guard points of Raqqa’s Internal Security Forces.
During the ensuing clashes, he said, one of the attackers was killed and another arrested. SDF and Internal Security Forces units are searching for the remaining attackers, he said.
The Syrian Observatory for Human Rights, a Britain-based opposition war monitor, reported that the attack targeted an area containing the headquarters of the SDF’s Internal Security Forces, anti-terrorism units, and a military intelligence prison where about 200 IS prisoners are housed.
The observatory noted that the attack was the 16th operation carried out by suspected IS sleeper cells in SDF-controlled areas since the beginning of this month.
The Islamic State group’s territorial control in Iraq and Syria was crushed by a years-long U.S.-backed campaign, but its fighters continued with sleeper cells that have killed scores of Iraqis and Syrians in past months.
Also on Monday, the observatory and the National Front for Liberation, a coalition of Turkish-backed rebel groups reported that six members of the coalition were killed in clashes with the SDF and the Syrian army in the Aleppo countryside.
Abdi cast blame for the IS attack in Raqqa partially on Turkey, which has carried out a campaign of airstrikes against the SDF in northeast Syria since late November and threatened a ground operation.
Abdi said the “terrorist activity coincides with the continuous Turkish threats to target the security and stability of the region.”
Ankara blames Kurdish groups in Syria for a deadly Nov. 13 explosion in Istanbul, an allegation the groups deny.
SDF units briefly halted joint anti-IS patrols with U.S.-led coalition forces due to the Turkish strikes but resumed them earlier this month.
Last week, U.S. Central Command said that American forces had arrested six Islamic State group militants in three raids in eastern Syria. The SDF said separately that its fighters had detained an IS militant who managed cells in eastern Syria.
Associated Press writers Ghaith al-Sayed in Idlib, Syria, and Abby Sewell in Beirut contributed to this report.
