"On January 2, the Facebook page 'Diana Arutyunyan' published information according to which Prime Minister Nikol Pashinyan congratulated the United States for its actions against a senior Iranian military official," Armenia's SNB security service said in a statement.

This "false information" was picked up by Azerbaijani and Iranian media, causing "major damage to the national security interests of Armenia", it said.

Pashinyan, who came to power after a 2018 revolution, himself denied on his Facebook page on Sunday that he had congratulated Trump.

He also urged the United States and Iran to exercise restraint while the foreign minister called his Iranian counterpart to express condolences over the assassination.

General Qasem Soleimani, Iran's top military commander, died in a US drone attack at Baghdad airport on Friday, raising tensions in the Middle East.

"Diana Arutyunyan" is the pseudonym for a man whose identity has not been revealed.

In a video released with the SNB statement, the man explained that he had created the Facebook page in 2018 to "write political publications" and admitted being the author of the article in question.

"I did it because I have political opinions and I believe that it is unjust to keep Robert Kocharyan in prison," he said in the video, referring to the former president who is being held for a "breach of constitutional order".

Landlocked Armenia has strained relations with neighbours Azerbaijan and Turkey. Maintaining strong ties with Iran is therefore crucial for Yerevan, which remains close to the United States, home to a vast Armenian diaspora.