Gunmen in a speeding car, their faces obscured by checkered headdresses, killed 15 persons and wounded at least eight today when they fired into a beach crowd, a restaurant and several shops in the port city of Tripoli in Syrian-occupied northern Lebanon.

It was the bloodiest rampage this year in Tripoli, Lebanon's second-largest city, which is encircled by Syrian soldiers.

The reason for today's attacks was not immediately clear, although Lebanese officials and privately owned Beirut radio suggested that they had been carried out by anti-Syrian Sunni Moslems to avenge the fatal shooting of one of their comrades.

There have been several such incidents this week in sunny, palm-dotted Tripoli, which residents now liken to West Beirut in the especially violent days when an array of warring militias held sway.

A Tripoli businesswoman commented that it is the custom for robberies to begin in the morning and shootings in the afternoon.

Sometimes, she said, the gunfire is aimed at no particular target, but when someone is hit, the battles begin.

This week has been especially bloody.

On Monday, youthful gunmen in civilian dress, their faces covered with the black-and-white-checked kaffiyehs, were manning submachine guns and rocket-propelled grenade launchers on a shoulder of the main highway, just south of the city and across from a Syrian checkpoint.

They stopped two American reporters and then allowed them to pass, but it was later learned that eight Lebanese had been kidnaped.

On Tuesday, pro-Syrian and anti-Syrian militiamen dueled with rocket-propelled grenades and machine guns. The fighting died down at night after paralyzing life in the city for most of the day. Schools and shops shut down early as residents hurried home.

Three persons were killed in those clashes, one a man hit by sniper fire who was left to bleed to death after he was trapped in an area being rained on by bullets.

A group called the Higher Coordination Committee, headed by Lebanese ex-prime minister Rashid Karama, was formed earlier this year to maintain the peace and keep rival gunmen apart.

It has performed its mission only intermittently. Karama, while respected, is thought to be unable to influence the situation strongly because he does not have a militia of his own to project power.

Residents also said Syrians soldiers are sometimes targets.