Russian security authorities announced on Friday the arrest of seven members of an ISIS terrorist cell. The Federal Security Service, or FSB, said the suspects were plotting a suicide bombing and a series of other explosions in St. Petersburg’s busiest areas this coming weekend Interfax news agency reported that the suspects were arrested in St. Petersburg on December 13 and 14. FSB said that a search of an apartment in the city found explosives, automatic weapons and extremist literature. It said the suspects had received instructions from ISIS. Earlier this week, the FSB said it arrested several ISIS-linked suspects in Moscow where they were plotting a series of suicide bombings during the New Years holiday season. In April, a suicide bombing in the St. Petersburgs subway left 16 dead and wounded more than 50.