MANAMA, BAHRAIN, DEC. 18 -- Iraqi warplanes attacked a loaded supertanker in the Persian Gulf today, forcing it to run aground off Iran, shipping sources said.

Iranian gunboats fired on two tankers ferrying Kuwaiti and Saudi Arabian oil in the southern gulf, setting one ablaze. Kuwait and Saudi Arabia are allies of Iraq, which has been at war with Iran since 1980.

There were no reports of casualties in any of the attacks.

Iran's official news agency said the Iranian Navy intercepted 19 merchant vessels yesterday, an unusually high number, but let them go after finding no Iraqi war cargo. It gave no further details.

The Lloyd's Shipping Intelligence Unit said missiles from Iraqi jets hit the supertanker Free Enterprise, which flies the Maltese flag. The vessel, carrying a full cargo of oil from Iran's Kharg Island terminal, was grounded, according to the accounts by Lloyd's and the shipping sources.

Iraq did not report any such raid. Both sides in the war have stepped up shipping attacks, with 18 vessels reported hit this month.

Two Iranian gunboats fired rocket-propelled grenades and cannons at the Liberian-registered Saudi Splendour, knocking out its radar, shipping executives said. The ship was forced to stop, as tankers cannot sail at night without radar, they said.