BEIRUT, Lebanon (AP) _ Shiite Moslem militiamen clashed with Palestinian guerrillas in south Beirut Monday despite a Syrian-brokered cease-fire in the 11-day-old war for the control of the Sabra and Chatilla refugee camps.

Palestinian sources reporting from Chatilla said one civilian was killed and three were wounded.

The fighting broke out when a Shiite Amal checkpoint near the entrance to Sabra stopped Palestinian women and confiscated food and cigarettes they were taking into the camp.

The new casualties brought the overall toll in the camps conflict since March 28 to 47 killed and 182 wounded.

Meanwhile, an extremist group warned Monday that it will bomb Italian cities unless the Rome government frees two Lebanese held on terrorist-linked charges.

A statement signed by the Front for the Defense of the Arab Political Prisoners in Europe said: ''Our patience has run out.

''We will not tolerate any delay after today. We warn that Italian streets shall witness tragedies similar to the French streets.''

That was a reference to a string of bombings in Paris last month. They were claimed by anonymous callers purporting to speak for the Committee of Solidarity with Arab Political Prisoners. It is believed linked to the Front.

''Let the Italian government know that it's repeated ignoring of our just demands is the reason for placing her subjects in the Arab world and Western Europe in constant danger,'' the hand-written Arabic-language statement said.

The statement, left in the mailbox of a Western news agency in Beirut, concluded: ''He who warns is excused.''

The statement identified the prisoners held in Italy as Josephine Abdo and Sarkis Abdallah Mansouri, ''who have been imprisoned for more than a year and a half now.''

In south Lebanon, gunmen killed two prominent Communist Party officials in the southern port of Tyre and in the market town of Nabitiyeh, 18 miles to the east.

The two men were identified by police as Kamel Sabbah, a high-school teacher in Nabatiyeh, and Khodor Jouneh, a full-time party worker.

No one claimed responsibility for the shooting. But there has been increasing friction between the pro-Palestinian Communists and Shiite zealots in the south.

Last month the two factions fought in a day-long battle in Beirut's mainly Shiite-populated southern suburbs after scores of communists and radicals of the Shiite Hezbollah, or Party of God, were kidnapped by both sides.

Also Monday, British Ambassador John Gray appealed for the release of two Britons missing for 11 days, indicating he believed the teachers have been abducted in kidnap-plagued Moslem West Beirut.

Gray said the embassy still has no word on the whereabouts of Leigh Douglas, 34, and Philip Padfield, 40, who were last seen leaving a popular Beirut bar on Good Friday.

No one has claimed responsibility for their abduction.

Forty-six foreigners have been kidnapped in the past two years in militia- ruled west Beirut.

Twenty-six have been freed, the bodies of three have been found and 17 are still missing, including six Americans and eight Frenchmen.