Iranian Supreme Leader Ayatollah Ali Khamenei on Saturday blamed recent protests in Iran on foreign “enemies” seeking to overthrow the government in the Islamic Republic.

Also, he said, enemies were waging a “psychological war” against Iran by accusing it of piracy for seizing two Greek ships after the United States confiscated Iranian oil from a tanker.

“Today, the enemies’ most important hope for striking a blow at the country is based on popular protests,” Khamenei said, referring to week-long protests over the collapse of a building in southwestern Iran last month that killed 37 people.

“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 1979 Islamic revolution, Ayatollah Ruhollah Khomeini.

Authorities have blamed the collapse of the 10-storey residential and commercial building in Abadan on local corruption and lax safety and say 13 people, including mayors and other officials, have so far been arrested for construction violations.

Protesters, however, say the disaster stemmed from government negligence and entrenched graft and have chanted slogans against officials, including Khamenei.

Iran residents have reported disrupted internet services, an apparent attempt to stop the use of social media to organise rallies and disseminate videos. Authorities have warned people to follow just official media and eschew “rumours” from social media.

The United States, which has imposed tough sanctions on Iran, confiscated the Iranian oil cargo on the Iranian-flagged Pegas that Greece impounded off its coast in April. Tehran retaliated by seizing two Greek ships on May 27.

But, Khamenei said, world media accuse Iran of piracy. “Who is the pirate here? You stole our oil. We took it back from you. Taking back a stolen good is no theft.”