"The mosque and representative office of Seyyed Ali Akbar Ojaghnejad, representative of supreme leader (Ayatollah) Ali Khamenei in Baku, were sealed and closed today by order of the authorities of the Republic of Azerbaijan," Tasnim said, without giving further details.

Ojaghnejad has held the post since 1996, according to the website of his office, which is located inside the mosque.

Azerbaijan's interior ministry spokesman Eskhan Zahidov said in a statement that the move was necessary because of "a surge in Covid-19 cases in several locations in Baku" and that the mosque's operation had been "suspended temporarily".

Iran's embassy in Baku said in a statement on Tuesday evening that it had followed up on the matter via diplomatic channels, adding that there had been no advanced warning of the move.

Since mid-September, tensions have soared between the two neighbours, who share a 700-kilometre (430-mile) border.

On Friday, the Iranian army's ground forces began manoeuvres near the frontier, a move criticised by Azerbaijani President Ilham Aliyev.

"Every country can carry out any military drill on its own territory. It's their sovereign right. But why now, and why on our border?" Aliyev had told Turkish news agency Anadolu.

Iran invoked its "sovereignty" to dismiss Azerbaijan's concerns.

"Iran will not tolerate the presence of the Zionist regime near our borders," foreign ministry spokesman Saeed Khatibzadeh said, alluding to Iran's arch-foe Israel.

Israel is a major arms supplier to Azerbaijan, which last year won a six-week war with neighbour Armenia over the disputed Nagorno-Karabakh region.

Azerbaijan's foreign ministry spokeswoman Leyla Abdullayeva said Monday that Iran's claims were groundless.

"We reject the allegations of any third party's presence near the Azerbaijani-Iranian border, such allegations are totally baseless," she said.

Another recent bone of contention was Baku's decision to impose customs taxes on Iranian trucks crossing its territory to Armenia.

To avoid the route, Iran's roads ministry announced on Monday that it was sending a delegation to Yerevan to discuss the completion of a road that directly links Iran to Armenia.

The statement said Azerbaijan "currently controls 20 kilometres of this 400 kilometre road that runs from Norduz (in Iran) to Yerevan".

Iran was "ready to complete the remaining part of the road as soon as possible," said the statement, which called the road "strategic" for Iranian trade.