A strong, early-morning earthquake shook presidents and prime ministers attending a Costa Rican summit from their beds Saturday and killed eight people, including several who were frightened into having fatal heart attacks.

The Red Cross (search) said most of the eight victims died from heart attacks. None of the participants in the ongoing 21-nation Ibero-American Summit (search) was hurt.

The quake cracked major highways, toppled water towers and knocked pillars from under a house, causing it to collapse atop a parked car. The National Emergency Commission said 500 homes were damaged. Power lines also were downed in some areas.

The U.S. National Earthquake Information Center (search) said the quake, which hit at 2:07 a.m., had a magnitude of 6.2 and was centered 30 miles south-southwest of San Jose.

"We jumped from the bed like two cats," said Panama's first lady, Vivian de Torrijos. "We're going to be able to remember the summit with something like that."

Costa Rica's seismological observatory recorded more than 100 aftershocks of magnitudes reaching 4.6.

Most of those who died of heart attacks were elderly, including several people in their 90s. A 32-year-old Italian man also died, apparently when he lost control of his motorcycle, officials said.

Ecuadorean President Lucio Gutierrez told reporters that, when the quake shook him awake, he got dressed and went to stand in a doorway.

He said security men rushed to his room and those of other leaders.

At a hotel nearby, people sobbed with fear as they ran from their rooms.

Spain's King Juan Carlos and Queen Sofia and officials from 19 Latin American nations were attending the summit, which ended late Saturday. Six heads of state sent lower-ranking officials and some, notably the president of Mexico, reportedly left Friday night.