DUBAI, UNITED ARAB EMIRATES, OCT. 2 -- Iran and Iraq scored successful hits on each other's shipping today as Iran's parliament speaker told the young people of his nation to prepare for war with the United States.

During Friday prayers at Tehran University, Hojatoleslam Ali Akbar Hashemi Rafsanjani said there was a "great likelihood {that} we will get involved in a new front" in the Persian Gulf. He said that "there are plans afoot" to respond to the Sept. 21 U.S. attack on the Iran Ajr, an Iranian vessel that the U.S. Navy said was laying mines in the Persian Gulf.

The new attacks on gulf shipping began before dawn today when an Indian-flagged petrochemical tanker, the Spic Emerald, partially loaded with highly volatile ethylene, was sprayed by rocket-propelled grenade and machine gun fire just 15 miles off the harbor here.

The captain of the vessel, Ajay Kumar Verma, gave a dramatic account of the assault in a radio broadcast monitored here, saying a small speedboat opened fire and then pursued the tanker for 30 minutes as it fled toward the United Arab Emirates' coast.

The attackers, believed to be Iranians, fired rocket-propelled grenades that ignited one pipeline on deck and sent the crew scurrying for lifeboats. The captain said two unexploded grenades were recovered on the ship afterward.

"The ship was on fire for about one hour, but we managed to put out the fire on our own," the captain said in one broadcast.

In a later ship-to-shore conversation, the captain said the Spic Emerald "would have exploded" had one of the grenades penetrated the sealed ethelyene tanks. "There would have been nothing left," he added.

Soon after the attack, a British warship came alongside the Spic Emerald and accompanied it to an anchorage. "We felt very safe after that," the captain said in a radio broadcast.

Later, Iraqi warplanes struck a Cypriot-registered tanker, the Felicity, on a crude-oil shuttle run between Iran's oil port at Kharg Island and its auxiliary terminal at Larak Island in the southern gulf.

Lloyd's of London said the ship was hit and set ablaze while heading toward Kharg. Iraqi warplanes have hit a total of 12 tankers steaming to or from Iranian ports since Sept. 21.

An Iraqi missile attack yesterday on the Shenton Bluff, a 77-foot shrimp boat whose captain was killed in the raid, prompted the owners of the boat to withdraw the rest of their fleet from the area.

A spokesman for the company, an Arab-Australian joint venture, said it will lose $250,000 a day by having to pull the fleet out of Iranian waters, where the boats were harvesting this season's shrimp crop under contract to the Iranian government.

The Australian government delivered a strong official protest to Iraq today in Canberra over the incident, in which Australian captain Robert Wilcox was killed.

France, meanwhile, announced its mine-sweepers operating south of the gulf in the Gulf of Oman found a Soviet-made mine off the port of Khor Fakkan, in the United Arab Emirates.

Also today, the Japanese Ministry of Transport said Japanese-flag ships operated by Japanese seamen would boycott further voyages into the gulf until greater safety measures were undertaken to protect them from attack.

Two vessels bound for Japan were raked with rocket and machine gun fire Wednesday. There are currently 21 ships with either Japanese ownership or crews in the gulf. Japan gets half of its oil from Persian Gulf states.

{The Turkish Foreign Ministry announced Friday that Iran and Iraq would close their diplomatic missions in each other's country, maintaining interest sections through the Turkish embassies in Tehran and Baghdad, The Associated Press reported. Despite their seven-year-old war, Iran and Iraq had up to now maintained diplomatic ties.}