MANAMA, Bahrain (AP) _ An Iranian warship blasted the back out of a Romanian-flag freighter in the gateway to the Persian Gulf today, setting it ablaze and critically injuring two crewman, gulf-based salvage executives said.

They said another commercial ship in the vicinity was hit by rocket- propelled grenades almost simultaneously and also caught fire.

The attacks brought to four the number of commercial ships struck by Iran in the gulf in the last three days.

The Romanian-flag 8,850-ton freighter Fundulea was headed for Kuwait when it was hit. The 16,859-ton container vessel Uni-Master, which flies the Panamanian flag, was en route to Saudi Arabia.

Both were attacked in the Strait of Hormuz.

The Fundulea, which was hit with cannon fire, burned for about five hours after the morning attack, said the salvage executives, who spoke on condition of anonymity.

Its crew abandoned ship after its master, second officer and cook were injured, they said.

Tugs rushed from the United Arab Emirates and Oman and helped extinguish the blazes on the Uni-Master, whose crew remained aboard, the sources said

The injured from the Fundulea were taken by helicopter to the United Arab Emirates and rushed to the Ras al-Khaimah hospital, where the master and second officer were reported in critical condition. The cook's injuries were minor.

The cook identified himself to reporters who visited the hospital. He said ship was carrying marble.

At least one Iranian warship, probably a frigate, was involved in the attack on the Fundulea and possibly on the Uni-Master, the salvage executives said.

The Iranian navy often intercepts vessels in the strait to see if they're carrying war materials for Iraq, its enemy in a 7-year-old war.

The executives said an Iranian vessel radioed the Uni-Master demanding its identity and destination.

The vessel had a Chinese crew ''who most likely could not communicate with the Iranians,'' said a Dubai-based radio monitor. ''They did not respond and were attacked.''

The Fondulea's captain identified his ship for the Iranian's and disclosed its destination. He was told he could proceed, but ''five minutes later, the Fundulea was attacked,'' the radio monitor said.

The Uni-Master, owned by the Taiwan-based Uniglory M company, was badly damaged. ''The superstructure of the vessel is gone,'' the monitor said.

The extent of damage to the Fondulea was not immediately known.

About 400 vessels of different nationalities have been attacked in the Persian Gulf in the war between Iraq and Iran.

In the past two weeks, Iraq claimed to have struck more than 20 vessels off the Iranian coast. Shipping sources have confirmed 10 of those attacks.

Iran said Sunday its navy fired on U.S. helicopters that tried to prevent the interception of a Greek vessel in the gulf. U.S. Navy officials denied the report.

The interception of the 29,108-ton Jimilta occurred Saturday, the official Islamic Republic News Agency said. IRNA also quoted Iran's navy commander as saying a gunboat fired on four U.S. helicopters that came to the scene.

No damage or casualties were reported.

Shipping sources said the Iranians attacked another Greek-flagged vessel Sunday in retaliation for Iraqi bombing runs.

An Iranian gunboat attacked the 63,953-ton tanker Andromeda in the southern gulf early Sunday. Rocket-propelled grenades damaged the Andromeda's hull but caused no casualties, the officials reported.

In West Germany, a published report said the United States asked the Bonn government to give more political and military support to American military actions in the gulf.

The U.S. requests were contained in two ''priority lists'' sent to Bonn by Lt. Gen. Dale. A. Vesser, director of strategic planning and policy of the U.S. Joint Chiefs of Staff, the magazine Der Spiegel reported.

America wants to use its military facilities in West Germany to support its actions in the gulf, the report said. The West German military was also expected to fly military supplies to the gulf if necessary, the magazine said.

In Abu Dhabi, United Arab Emirates, Foreign Minister Ali Akbar Velayati of Iran made a brief stopover today and discussed official U.N. bids to end the gulf war.

The defense ministers of the Gulf Cooperation Council, meeting there Sunday, stressed that their own security was ''indivisible'' and said world peace was threatened by the war.

The ministers, representing Saudi Arabia, Kuwait, Qatar, Bahrain, Oman and the United Arab Emirates, ''agreed to deepen military cooperation,'' a statement said.

It did not elaborate.