WASHINGTON - The US Treasury Department imposed sanctions on the Iranian petrochemical industry Friday in an attempt to further derail Iran’s alleged nuclear weapons programme.

The department said one petrochemical company had “aided Iran’s efforts to evade sanctions by attempting to conceal oil transactions with the government of Iran and an aircraft procurement network supporting Iran’s airlines that previously have been sanctioned for involvement in Iran’s support for terrorism.”

With sanctions already imposed on Iran’s oil business, which funnels most of its revenue through the central bank, the Treasury said it is targeting sanctions evaders.

The Treasury listed eight companies that are owned or controlled by the government of Iran, including Bandar Imam Petrochemical Co., Bou Ali Sina Petrochemical Co., Mobin Petrochemical Co. and Tabriz Petrochemical Co.

Besides targeting Iranian companies, the Treasury said it was sanctioning two companies “for knowingly engaging in a significant transaction for the purchase or acquisition of petrochemical products from Iran.

The new steps came a day after the administration issued sanctions against a top aide of Iran’s supreme leader, Ayatollah Ali Khamenei, and more than 50 other Iranian officials for what it called their efforts to repress dissent and free speech in Iran, where presidential elections are scheduled in two weeks.