NICOSIA, CYPRUS, DEC. 20 -- Iran and Iraq reported today that their armies had clashed near the southern Iraqi city of Basra, but the reports differed sharply about the outcome of the fighting.

It was difficult to determine the exact scope of the clashes from the vague communiques issued by the two sides, but they suggested that the fighting, although serious, was on a relatively small scale.

Western military analysts have been reporting for weeks that Iran has carried out a build-up of volunteers southeast of Basra and have predicted a major offensive in the next month aimed at capturing the city, Iraq's second-largest.

The analysts also predicted that Iran would begin the campaign with a series of false attacks aimed at throwing the Iraqis off balance and also at drawing troops away from the defense of Basra.

Based on the official versions of the latest fighting, the clash may have been such a feint.

First word of the fighting came from Iraq, which said its forces had repelled an Iranian attack with an estimated two brigades -- about 5,000 to 7,000 men -- in the Zubaidat area north of Basra.

An Iraqi communique released in Baghdad said "the bulk of enemy units" were destroyed by the Iraqis, but gave no exact casualty figures.

Iran said four Iraqi battalions were 50 percent to 80 percent destroyed by the fighting Saturday night, adding that all Iranian forces returned safely to their bases.

The official Iranian news agency said heavy casualties were suffered by the Iraqis and denied that any Iranian brigades had been destroyed.

The accuracy of the communiques could not be verified.

What appeared to be most significant in the claims was the fact that heavy ground fighting in the war has resumed after an interval of nearly nine months.