SAN JOSE - RESCUE teams struggled in rain and mist on Friday to reach hundreds stranded in mountainous central Costa Rica, including some 400 tourists, after a strong earthquake that left at least four people dead.

Dozens remained unaccounted for as the Costa Rican Red Cross lowered its death toll from 14 to four from Thursday's magnitude 6.1 earthquake, the strongest to shake the country in the last 150 years. Several aftershocks followed the quake.

'Problems with a radio communication from a rescue patrol' in the Poas volcano area near the epicenter of quake led the Red Cross to take for dead 10 people who were in fact missing, a spokesman for the humanitarian organisation said.

The quake rocked the Central American nation on Thursday, collapsing homes in and around the capital and setting off landslides that blocked major highways.

Two sisters who had been selling sweets died in a landslide near the epicenter. Another woman died of a heart attack in a San Jose suburb and a 12-year-old girl was crushed by a wall in her home near the volcano.

'These losses of life fill us with pain; our prayers will be for their families,' President Oscar Arias said on Thursday, noting that 'hundreds of families had seen serious damage to their homes'.

The president was due to visit the quake zone on Friday, as cracked roads, fallen trees and earth impeded rescue efforts in the farming region home to popular tourist sites.

Rescue teams desperately searched for victims around the Poas volcano throughout the night and warned that the death toll could rise on Friday.

Hundreds of people remained stranded in the Vara Blanca and Cinchona areas, close to the volcano.

Some 400 tourists were trapped in a hotel near La Paz waterfalls that was cut off from roads by a landslide.

Hundreds of others spent the night in schools or in roadside stalls after their homes were destroyed in the lush agricultural zone.

The National Emergency Board on Thursday declared a red alert in the metropolitan area of the central valley where 2.5 million of the country's four million people live, including San Jose, Cartago, Alajuela and Heredia.

Search helicopters ferried rescued people in need of medical care to local hospitals, while the US army was due Friday to send two Blackhawk helicopters, based in Honduras, to help with the operations.

The government contracted most private helicopters in the country, which has no army.

The quake hit at 1.21 pm (3.21am Singapore time) on Thursday, some 30 kilometres northwest of the capital, shaking water out of swimming pools.

It was felt across the country, a popular ecotourism and beach holiday destination, as well as in neighboring Nicaragua to the north.

San Jose residents reported broken windows, cracks in buildings, ceilings and roads.

Amid scenes of panic, public buildings were evacuated and the city's international airport briefly suspended all flights. -- AFP