Six persons, including four Shiite Moslem guerrillas who apparently were suicide bombers, were killed today when explosives strapped to the Shiites' bodies detonated at an American-financed fundamentalist Christian radio station in southern Lebanon, about a mile from the Israeli border.

A guard of the Israeli-backed South Lebanon Army and a civilian broadcasting technician inside the station were killed in the attack, the Israeli Army command said. The building was damaged heavily by the estimated 200 pounds of explosives carried by the four men, Israeli military sources said.

An Army source said two SLA guards posted at the radio station opened fire on the guerrillas as they ran toward the building and may have detonated the explosives carried by one of the attackers. The others apparently detonated their explosives as they neared the building, he said.

There were conflicting accounts of the sequence of events in the attack, with an SLA spokesman telling Israeli radio tonight that the "saboteurs" may have intended to escape after the attack.

"They were trying to leave, but had a skirmish" with the guards inside the building, "which delayed their pullout from the area. In the meantime, the charges exploded," the SLA spokesman said.

The station, which calls itself the "Voice of Hope," went back on the air tonight, using equipment borrowed from its television affiliate, which also broadcasts throughout Lebanon, from a transmitter near the site of the explosion. A Voice of Hope spokesman, Isaac Gromberg, said the heavily damaged building, which housed studios and offices, will be rebuilt with donations raised in the United States.

The blast occurred near where 12 Israeli soldiers died on March 10, when a suicide truck-bomber drove into a troop convoy. That was the most costly guerrilla attack on Israeli forces since a suicide car-bomber blew up the military headquarters at Tyre in November 1983, killing 29 Israeli soldiers and 32 Lebanese being held there.

Asked how a squad of Shiite guerrillas could travel undetected so close to the Israeli border, an Israeli military source said they probably came from Khaim, a mostly Druze village in the hills above the radio station.

"It is not too much for them to walk at night to this place," the official said. The attack occurred shortly after 1 a.m.

The radio station, owned and operated by an American missionary organization called High Adventure, began broadcasting in September 1979 with the financial support of Israel after the Israeli Army installed a forerunner of the SLA as an allied force to control the area.

The station was founded by George Otis, a former general manager of the Learjet Corp. who runs a Van Nuys, Calif., evangelical mission called High Adventure Ministries.

The Voice of Hope transmitters beam a mixture of country music, inspirational messages from the Old Testament and news broadcasts favorable to the SLA and the continued Israeli Army presence in southern Lebanon.

Before the June 1982 Israeli invasion, residents of Lebanese villages just north of the Litani River that were inhabited by Palestine Liberation Organization guerrillas would refer to the station as the "Voice of Death" because the late Maj. Saad Haddad, who then headed the pro-Israeli militia, frequently would go on the air and announce artillery bombardments of the villages a few minutes before opening fire.

Because the Voice of Hope is financed and controlled by Americans, Lebanese officials long have bridled at what they regard as U.S. government connivance in broadcasting pro-Israeli messages in Lebanon in violation of the state monopoly that ostensibly controls airwaves throughout the country.

In practice, however, the monopoly is breached routinely by radio stations controlled by a myriad of warring factions in Beirut.