The sanctions, which include a ban on trading with the companies, come days after Iran test-fired a 1,300km-range missile capable of striking Israel.

The involvement of two other companies is still being examined and they could face similar punishment if the US decides they were also implicated.

Investigations into the case were started by the Russian authorities. Mr Clinton said he was encouraged by the action the country has taken against the proliferation of weapons of mass destruction.

The sanctions order expands the president's authority to act against firms anywhere in the world that sell weapons of mass destruction and rockets capable of carrying chemical, biological and nuclear weapons.

Missile test raises tensions

The missile, whose launch was detected by US spy satellites, is though to be a Shehab-3 of North Korean design

On Sunday, the Iranian Defence Minister, Ali Shamkani, said that the test was carried out through the efforts of Iranian military experts and without "any foreign support".

He added: "The defence policy of the Islamic republic is based on improving its deterrent capability."

However, the test drew strong criticism from the US. President Clinton warned it could be an obstacle to Washington developing better relations with Teheran.