Iran told all volunteers Wednesday to report for duty and put its bases on alert to face what it called "bestial aggression" from the United States and Iraq. Kuwait said Iran fired a missile into its territory before dawn.

Iran said it launched a new thrust into northeastern Iraq, and both Iran and Iraq reported exchanging air strikes.Shipping executives said commercial vessels were avoiding the Persian Gulf, and Iranian warships were reportedly staying in port.

The U.S. Navy sank or damaged six Iranian vessels and destroyed two offshore oil platforms Monday in the heaviest fighting with the Iranians since the U.S. Navy began escorting Kuwaiti ships in the gulf last July.

Kuwait's Defense Ministry gave no details of where the "Scud-type" missile exploded Wednesday or whether it caused casualties or damage.

A source who spoke on condition of anonymity said the missile fell near desert oilfield operated by Getty Oil in the vicinity of Wafra, which is on the Saudi border.

The Scud is a Soviet-designed surface-to-surface missile with a range of about 180 miles. Iran has used such missiles against Iraq in the 71/2-year-old gulf war.

Iran last year fired several Chinese-made Silkworm missiles into Kuwait's coastal waters.

Tehran Radio, announcing the nationwide mobilization, declared: "Today our revolution and our heroic nation is faced with the onslaught of the evil triangle of America, Iraq and the reactionaries."

It said all volunteers should report to their bases throughout the country "and get ready for departure" to the battlefront. The broadcast did not mention numbers, but Iranian leaders have claimed more than 3 million Iranians have undergone military training in the last six months.

Iran's official Islamic Republic News Agency, monitored in Cyprus, said Iranian forces killed or wounded 300 Iraqis and captured more than 250 in the Shemiran mountain region of Kurdistan in the new offensive.

The search continued Wednesday for a U.S. Marine attack helicopter and its two-man crew, missing since going out on a night mission following Monday's fighting.

There was no estimate of Iranian casualties Monday, but Navy officers said they presumed them to be heavy.