At least 50 houses were wrecked by `a swarm of tremors' -- perhaps a dozen.

 BY GLENN GARVIN

 MANAGUA -- Earthquakes rattled up and down Central America for hours
 Thursday, leaving at least three dead and 32 more injured in Nicaragua, where the
 strongest tremor occurred.

 Nicaraguan civil defense authorities said the casualty count was likely to rise as
 they reached homes flattened by the quakes in small towns a few miles south of
 Managua.

 At least 50 houses were wrecked by what officials described as ``a swarm of
 tremors'' -- perhaps as many as a dozen -- that rippled through Nicaragua
 beginning at 3:30 p.m EDT. Two hours earlier, earthquakes shook El Salvador and
 Guatemala, but no injuries or significant damage were reported there.

 It was a different story in Nicaragua. The first tremor had a magnitude of 5.9, the
 second 4.0, and they were magnified because the quakes were barely half a mile
 underground, said the Nicaraguan Institute for Territorial Studies.

 The epicenter of the two biggest tremors was Lake Apoyo, located just outside
 the city of Masaya, about 20 miles south of Managua. But the tremors were felt
 all along the country's Pacific coast, from the Honduran border in the north to the
 Costa Rican border in the south.

 The impact was sharp in Managua as well, where hundreds of people raced into
 the streets. The city has been destroyed three times by earthquakes, including
 the devastating 1972 quake that killed about 11,000 people.

 The three reported fatalities Thursday were children. One was killed on the shores
 of Lake Apoyo and another in the nearby town of Catarina, both crushed by the
 collapsing walls of their homes. Details of the third death were unavailable.

 Tremors are a common occurrence in Nicaragua, but seismic activity has been
 steadily increasing over the past month, triggering worrisome activity at volcanoes
 that dot the Pacific coast.