DUBAI, UNITED ARAB EMIRATES, DEC. 23 -- Iran attacked a Norwegian oil tanker with rockets and set it ablaze in the southern Persian Gulf today, shipping sources said.

The sources said the 285,400-ton Berge Big was hit by seven rockets in two of its starboard tanks and was set on fire after having taken on oil at the Saudi port of Ras Tannurah.

They said it was taking on water after the attack at 10:50 p.m. local time (1:50 p.m. EST) as it was sailing 25 miles off the coast of Dubai but no casualties were reported.

A U.S. Navy helicopter in the area offered to lift off the crew, but the officers declined, the sources said.

The attack came 24 hours after an Iranian frigate hit the Liberian-flagged tanker Stena Concordia, the sources said.

This followed a long-range Iraqi air raid in which three supertankers were hit at Tehran's Larak oil terminal at the mouth of the gulf.

The sources said the Berge Big was heading for Dubai under its own power. Several firefighting tugs were on the way to offer assistance.

It was the 11th attack by Iran in two weeks and came as Arab leaders in the region pressed Iran to end its war with Iraq.

The Stena Concordia was hit in its engine room late yesterday, but no casualties were reported and the ship was able to proceed under its own power.

The Iraqi raid on Larak yesterday caused heavy damage to the crew quarters on the World Petrobras, used by Iran as a storage tanker for crude oil ferried from its Kharg Island terminal in the northern gulf.

Two other supertankers suffered minor damage, while the World Petrobras resumed pumping oil to foreign tankers today. It was reported yesterday that four supertankers had been hit.

It was the second raid on Larak in three months by Iraqi jets, which usually concentrate their attacks on shuttle tankers ferrying oil to the southern gulf from Kharg.

At least 26 of about 40 tankers involved this year in Iranian shuttle operations have been hit, shipping sources said. Five or six were total writeoffs, and 13 were still out of action.

In the Saudi capital of Riyadh, officials preparing for a gulf Arab summit opening Saturday said the Arab leaders would warn Iran against extending its war with Iraq.

The officials said the heads of the Gulf Cooperation Council states -- Saudi Arabia, Kuwait, Bahrain, Qatar, the United Arab Emirates and Oman -- were likely to urge the big powers, the Soviet Union in particular, to step up efforts to end the fighting.