BEIRUT (Reuters) - Security forces in southwest Iran have arrested four suspected Islamic State operatives who were planning attacks, Intelligence Minister Mahmoud Alavi was cited as saying by the Tasnim news agency on Tuesday.

Under Islamic State’s ultra-hardline Sunni Muslim ideology, Shi’ites are considered apostates. Last year, its members carried out attacks on the parliament in Tehran and the mausoleum of the founder of Iran’s revolution, Ayatollah Ruhollah Khomeini, killing at least 18 people.

“This team had the intention of sowing destruction in certain areas but the operations were not carried out because of the timely intervention of security forces,” Alavi said, according to Tasnim.

The group was led by a man whose brother was killed while fighting for Islamic State in Syria, Alavi said.

Separately, three suspected Islamist militants and one member of the Iranian security forces were killed when they clashed on Saturday in northwestern Iran, according to the Revolutionary Guards.