Iraq denied tonight an Iranian claim that its forces have captured Iraq's largest offshore oil-loading terminal in the Persian Gulf during a fierce weekend naval battle.

The clash, apparently among the war's biggest naval encounters, also assumed particular importance for both sides because an Iraqi defeat at Mina al-Bakr would represent the first time in the nine-week-old gulf war that the Iranians have seized Iraqi territory.

An Iraqi Army communique said the Mina al-Bakr terminal, about 15 miles off the Iraqi coastal town of Al Fao, is still under the control of its defenders, despite intense attacks by Iranian forces Friday night and yesterday. The Iraqis claimed that three Iranian warships and three F4 Phantom fighter-bombers were destroyed in the action.

"After despairing of realizing its aim of reaching Mina al-Bakr following battles waged by our naval and air forces over four days, the enemy brought in a frigate and our victorious forces destroyed it completely," the Iraqi statement said.

The official Iranian news agency, Pars, said Iranian naval forces destroyed or captured 11 iraqi gunboats and captured 20 Iraqi seamen in the battle.

[In Tehran, a car bomb exploded near the Iranian Foreign Ministry, slightly injuring four persons, including three children, a hospital spokesman said. Iranian officials told Reuter they did not know who was responsible.]

An Iraqi government official characterized the Mina al-Bakr attack as an attempt by the Iranians to boost the morale of their forces with a dramatic breakthrough into Iraqi sovereignty, since the war so far has been fought almost exclusively on Iranian territory.

"Also, they have been extremely frustrated that oil has been going out of there," said the official, who said the attack was probably linked to last week's bombing raids on the northern Iraqi petroleum complex at Kirkuk.

Iraq last week resumed shipping oil from Kirkuk through the trans-Turkey pipeline to Mediterranean coastal refineries.

Mina al-Bakr is the largest of the three oil-loading terminals in the Persian Gulf. It was built at a cost of $100 million with U.S. and West German assistance, officials said. The others are Kohr Amaja, also offshore, and a deep terminal shore facility at Al Fao.