Ayatollah Ali Khamenei, Iran's supreme leader, blamed recent protests in Iran on foreign enemies trying to overthrow the government in the Islamic republic.
He said enemies were waging a psychological war against Iran by accusing it of piracy for seizing two Greek ships after the US confiscated Iranian oil from a tanker.
The enemies most important hope for striking a blow at the country is based on popular protests over the collapse of a building in south-western Iran last month, which killed 37 people, Khamenei said.
But the enemies'calculation is as wrong as many earlier ones, he said in a televised speech on the 33rd anniversary of the death of the leader of Iran's Islamic revolution of 1979, ayatollah Ruhollah Khomeini.
The collapse of the 10-storey residential and commercial building in Abadan has been blamed for local corruption and lax safety, and authorities say 13 people, including mayors and other officials, have been arrested for construction violations.
Protesters say the disaster stemmed from government negligence and graft and have chanted slogans against officials, including Khamenei.
People living in Iran have reported disrupted internet services, an attempt to stop the use of social media to organise rallies and disseminate videos. People should follow only official media and avoid rumours from social media.
The US imposed tough sanctions on Iran, confiscated Iranian oil cargo on the Iranian Pegas that Greece impounded off its coast in April. Tehran retaliated by seizing two Greek ships on 27 May.
Khamenei said that the world media accuses only Iran of piracy. We took it back from you. He said taking back a stolen goods is not a crime.