The United States on Thursday imposed sanctions on several Iranian and Turkish companies and a number of aircraft in a move targeting four Iranian airlines.

The companies targeted were linked to Mahan Air and Meraj Air, the US Treasury Department said in a statement. It also said it was targeting a number of their aircraft, as well as aircraft from Caspian Airlines and Pouya Air.

The United States said the two airlines had ferried weapons, fighters and money to proxies in Syria and Lebanon. Washington also threatened sanctions for others granting landing rights and providing services to the aircraft.

“The deceptive practices these airlines employ to illegally obtain services and US goods is yet another example of the duplicitous ways in which the Iranian regime has operated,” US Treasury Secretary Steven Mnuchin said in a statement.

Read: EU could compensate firms hit by US sanctions over Iran

The sanctions were the latest in the United States’ efforts to economically strangle Iran with the hopes of blocking the country’s efforts to develop nuclear weapons.

Earlier this month, the United States withdrew from a 2015 nuclear accord that had lifted sanctions on Iran in exchange for curbs to its nuclear program, dismaying US allies.

On Tuesday, the United States imposed sanctions on five Iranians it said had provided Yemen’s Houthi movement with weaponry and expertise to launch missiles at cities and oil infrastructure in Saudi Arabia.