Battles between rival Shiite Moslem militias burst out of the southern slums Friday, filling neighborhoods that had been quiet for two years with the thunder of cannon and rocket fire.

In south Lebanon, Israeli warplanes blasted bases used by Palestinian guerrillas and allied Lebanese militiamen, killing five guerrillas and wounding 15 other people. It was the 23rd Israeli air raid in Lebanon this year.Fighting in Beirut pitted the mainstream Shiite militia Amal (Hope) against the pro-Iranian Hezbollah, or Party of God. Police said at least 10 people were killed and 20 wounded, most of them civilians, since the fighting began Thursday evening.

It was the first time the Amal-Hezbollah struggle for domination of Lebanon's 1 million Shiites reached the residential neighborhoods and once-glamorous hotel district of central Beirut.