Kurdish rebel leaders in northern Iraq are pleading for the U.S.-led allies to send food, saying they are now more worried about starvation than the offensive by Saddam Hussein's loyalist troops.

Iraqi forces Thursday reportedly launched a major air and artillery attack against the rebel-held oil city of Kirkuk."The Iraqi army has started a massive air attack on Kirkuk," said Latif Rashid, a spokesman in London for the Iraqi Kurdistan Front. He said there were casualties, but he had no details on the numbers.

Kirkuk, a city of 200,000 residents, was captured about a week ago by rebel fighters. The city is 150 miles north of Baghdad and is the most important city in the hands of Kurdish rebels fighting to topple Saddam.

Rashid claimed government forces were using Soviet-made MiG and Sukhoi aircraft, as well as helicopter gunships, light airplanes, surface-to-surface missiles and artillery in the assault.

The report could not be confirmed, but rebel groups said Wednesday that Iraqi forces were massing outside the oil center.

In another report on the Iraqi offensive in the north, Iraq's official news agency claimed Thursday government forces have recaptured Dohuk, a city 25 miles southeast of this rebel-held town. That report could also not be confirmed and Rashid denied the claim.

The Kurds in Zakho said Saddam's government is refusing to deliver U.N. food supplies to them and that Turkey and Iran were blocking shipments over their borders.

Saddam loyalists are widely reported to have retaken southern Iraq's major cities from Shiite Muslim rebels and are said to be moving reinforcements northward to confront the Kurdish fighters.

Quoting refugees from Iraq, Tehran Radio said fighting in and around Basra, Iraq's second largest city, intensified overnight and government troops Thursday brought in helicopter gunships, artillery and tanks to blast the city, destroying homes and killing many people.