Reuters reports that Iran has provided Russia with a large number of powerful surface-to-surface ballistic missiles, six sources told Reuters, deepening the military cooperation between the two U.S.-sanctioned countries.

Iran's provision of around 400 missiles includes many from the Fateh-110 family of short-range ballistic weapons, such as the Zolfaghar, three Iranian sources said.  This road-mobile missile is capable of striking targets at a distance of between 300 and 700 km, experts say.

 The shipments reportedly began in early January after a deal was finalized in meetings late last year between Iranian and Russian military and security officials that took place in Tehran and Moscow, one of the Iranian sources said.

An Iranian military official - who, like the other sources, asked not to be identified because of the sensitivity of the information - said there had been at least four shipments of missiles and there would be more in the coming weeks. He declined to provide further details.

Another senior Iranian official said some of the missiles were sent to Russia by ship via the Caspian Sea, while others were transported by plane.

“There will be more shipments,” said the second Iranian official.  “There is no reason to hide it. We are allowed to export weapons to any country that we wish to.”

A third source, familiar with the matter, reportedly confirmed that Russia had received a large number of missiles from Iran recently, without providing further details.

Iran's defense ministry and the Revolutionary Guards - an elite force that oversees Iran's ballistic missile program – reportedly declined to comment.

Russia's defense ministry did not immediately respond to a request for comment, according to Reuters.

U.N. Security Council restrictions on Iran's export of some missiles, drones and other technologies expired in October.  However, the United States and European Union retained sanctions on Iran's ballistic missile program amid concerns over exports of weapons to its proxies in the Middle East and to Russia.