BEIRUT, Lebanon (AP) _ An apparently pro-Libyan group in a communique published Sunday claimed responsibility for kidnapping two U.S. citizens in Moslem west Beirut last week, the second such claim in as many days.

The terse communique signed by the Arab Revolutionary Cells-Omar Moukhtar Forces also warned the United States against ''continuing its attacks on the Arab nations.''

The claim was published by the independent Beirut newspaper An-Nahar and the leftist newspaper As-Safir.

On Saturday, Christian-controlled Voice of Lebanon radio station quoted an anonymous telephone caller as claiming that the previously unknown group called the Khalaya al-Baath (Resurrection Cells) abducted Frank Herbert Reed on Tuesday and Joseph James Cicippio on Friday.

Omar Moukhtar is a Libyan national hero who fought Italy's colonial regime in the 1930s. His name has been used by several groups in claims of responsibility for bombing attacks on British and American targets in Lebanon.

A note signed by the Arab Revolutionary Cells was found near the gunshot bodies of a kidnapped American librarian and two British teachers found east of Beirut on April 18.

That note said the three hostages were ''executed'' by the group in retaliaton for the British-supported bombing raid on Libya.

It could not be determined whether the group claiming responsibility for the recent abductions was the same as the group which claimed to have killed Peter Kilburn, 61, of San Francisco; and Britons Leigh Douglas, 34, and Philip Padfield, 40.

There was no way of verifying the claim reported by the Voice of Lebanon, which speaks for President Amin Gemayel's right-wing Phalange Party and rarely has been accurate on responsibility claims for terrorist attacks in west Beirut.

It said the Arabic-speaking caller warned against any ''aggression on Syria'' and added, ''We give Americans living in west Beirut a period of two weeks to leave. Otherwise they will be kidnapped.''

Al-Baath is the name of Syrian President Hafez Assad's political party, which has strained relations with the Phalange.

On Friday, the Voice of Lebanon said Hezbollah, or the Party of God, a fundmentalist Shiite Moslem group, was responsible for Reed's abduction. It said Reed's kidnappers smuggled him to Baalbek in east Lebanon's Syrian- controlled Bekaa Valley.

Fewer than 30 Americans are believed to be living in the divided capital's Moslem sector. East Beirut is predominantly Christian.

Reed, 53, director of the Lebanese International School in west Beirut, was kidnapped by four gunmen Tuesday while driving to a golf course at the city's outskirts.

Cicippio, 56, who was born and grew up in the Norristown area of Pennsylvania, was seized by four gunmen when he left his apartment on the American University of Beirut's campus in west Beirut. He is the school's acting comptroller.

Both Reed and Cicippio converted to Islam to marry Moslem wives.

An American who visited Mrs. Cicippio's apartment Saturday and identified himself only as a neighbor told reporters she ''is in very bad condition.''

''She just can't see reporters,'' he said. ''Please understand. She's still in a state of shock.''

Lebanese and Syrian troops were patrolling the American University of Beirut on Saturday, and police were checking the trunks of vehicles at the university's gates.

The university has been plagued by kidnappings and assassinations since Moslem militias wrested control of west Beirut from the Lebanese army in February 1984.

In July, Syria sent troops to west Beirut to help try to end militia reign. There has been a resurgence, however, of abductions, car bombings and bank robberies.

There are 18 foreigners now missing in Lebanon: Six Americans, seven Frenchmen, two Britons, an Italian, an Irishman and a South Korean.

The fundamentalist Islamic Jihad, of Islamic Holy War, says it is holding three American hostages: Terry A. Anderson, 38, born in Lorain, Ohio, chief Middle East correspondent for The Associated Press; David Jacobsen, 55, of Huntington Beach, Calif., director of the American University Hospital in Beirut, and Thomas Sutherland, 55, the university's acting dean of agriculture.

Islamic Jihad said it killed another American hostage, U.S. diplomat William Buckley, but the body was never found.

In another development, a group calling itself the Arab Fedayeen Cells claimed responsibility on Saturday for the bombing of a British bank in Christian east Beirut.

The explosion Friday at the British Bank for the Middle East wounded a pedestrian, damaged the bank's entrance and shattered windows.

The group, whose name indicates it is pro-Libyan, made the claim in a typewritten statement in Arabic dropped in the mail box of a Western news agency in west Beirut.