U.S. President Barack Obama has signed an executive order imposing tougher sanctions on Iran and its central bank.
In a statement accompanying the order, Obama said the sanctions were necessary because the Central Bank of Iran and other Iranian banks were concealing transactions with sanctioned parties and because of the "unacceptable risk" posed to the international financial system by Iran's activities.
The executive order prevents any assets deemed to be in U.S. control -- including in foreign branches of U.S. banks -- from being transferred, paid, or withdrawn.
The sanctions were passed by Congress late last year.
The United States and the European Union are seeking to pressure Iran through sanctions to abandon its nuclear activities which Western powers suspect are aimed at making atomic weapons.
Iran denies any such intentions.
Compiled from agency reports