DAMASCUS, SYRIA, AUG. 24 -- Irish hostage Brian Keenan was freed by his Lebanese captors today after more than four years in captivity.

Keenan, the fifth Western hostage released by Islamic fundamentalist captors in Beirut in five months, was taken from Beirut to Damascus. Syrian officials said Keenan, 39, would be handed over to Irish Foreign Minister Gerry Collins on Saturday.

Iran, which has considerable influence among Shiite Moslem fundamentalist groups in Lebanon, said it had worked for months to help secure the release.

A group calling itself the Organization of the Islamic Dawn announced the release in a terse, typewritten Arabic statement delivered to the Beirut newspaper an-Nahar. "We have decided to release Irish hostage Brian Keenan," it said. "This was done at exactly 9 p.m. Beirut time" (2 p.m. EDT).

Until today, no group had claimed responsibility for kidnapping Keenan.

Keenan was freed in Moslem west Beirut. {He arrived in Damascus later tonight, and Syrian officials said he would spend the night in a government guest house in the capital, Reuter reported.}

Keenan was kidnapped by gunmen on April 11, 1986, in west Beirut while walking to the American University of Beirut, where he taught English. He was born in Belfast, Northern Ireland, and was traveling on an Irish passport, but is also a British citizen.

Thirteen Westerners -- six Americans, four Britons, two West Germans and an Italian -- are still believed held by extremist Shiite Moslem groups in Lebanon. Most have been held more than three years; Terry Anderson, chief Middle East correspondent for the Associated Press, has been held since March 16, 1985.

Today's statement by the Organization of Islamic Dawn was just the second it has made on hostages. On April 30, it said it was freeing U.S. hostage Frank Reed. The Malden, Mass.-born educator was released that day.

Hostage Robert Polhill of New York was freed on April 22, and two Swiss Red Cross workers, Elio Erriquez and Emmanuel Christen, were freed this month.

Reed, held 3 1/2 years, said after his release that he had been with Keenan. Reed's wife, Fifi, said Friday that her husband would fly to Ireland later to meet with Keenan.

Keenan's sister, Elaine Spence, burst into tears at the news of her brother's release. She and another sister, Brenda Gillham, had driven from Belfast to Dublin today to meet Foreign Ministry officials as speculation grew stronger that after many disappointments their brother was to be freed.

The Iranian news agency IRNA had reported Thursday that a European hostage would be released soon. Today, Iran's deputy foreign minister, Mahmoud Vaezi, told the Tehran Times newspaper that Keenan would be released and said: "We are thankful to the Islamic groups in Lebanon who once more showed their goodwill toward the West."

Vaezi said the release resulted from "several months of efforts of the Iranian officials and Islamic groups in Lebanon."

"We expect that the West will take similar steps for the freedom of Lebanese prisoners and Iranian hostages. Such a move will make our efforts for the freedom of hostages easier."

Iran has linked the fate of Western hostages to that of four Iranians kidnapped by Christian Lebanese Forces militiamen in July 1982. The four are widely believed to have been killed. But Iranian leaders have stressed that they would use their influence to help free Western hostages in exchange for help in freeing the Iranians.

{The Church of England said Keenan's release might mean other Western hostages held in Lebanon would be freed, Reuter reported. John Lyttle, a spokesman for the Archbishop of Canterbury, whose special envoy Terry Waite was kidnapped in Beirut in 1987, said in London that the release was good news for the families of all the hostages.

{The United States said it welcomed Keenan's release and continued to urge the release of all hostages in the Middle East, Reuter said. State Department spokesman Richard Boucher told reporters, "We're all glad when somebody gets out. We continue to urge the immediate release of all hostages."}

Keenan was dubbed Britain's "forgotten" hostage because his plight did not receive the same publicity as that of Waite and British television journalist John McCarthy. Keenan spent most of his life in strife-torn Belfast, and he dismissed the dangers of Beirut when he went there to teach in 1986.