A magnitude 5.1 quake killed at least eight people in southern Spain on Wednesday, sending historic buildings crashing down as panicked residents fled for their lives.

Eight people perished in the deadliest tremor in Spain in more than five decades, a spokeswoman for the regional government of Murcia said, revising down an earlier toll of 10 dead without explanation.

The quake collapsed fronts of buildings in the southeastern town of Lorca and ripped open walls, which slumped into the streets.

Witnesses reported many injuries.

A church clocktower smashed to the ground and narrowly missed one television reporter as he conducted an interview in the town on Spanish public broadcaster TVE. A bronze bell lay in the rubble.

Fearful residents including families with children gathered outside with blankets as night fell. About 10,000 people were evacuated from the cordoned-off city-centre.

"We are calling on shopping centres in the area to give them water, food and blankets," Lorca mayor Francisco Jodar said.

Television images showed shocked families with children gathering in squares and playgrounds, some weeping and hugging as they sought safety. Masonry blanketed streets and a line of parked cars lay crushed under tonnes of rubble. A corpse lay in the street covered in a rescue blanket.

The tremor struck at 6:47 pm (1647 GMT) with a depth of 10 kilometres (six miles) and could be felt as far away as the capital Madrid. It hit nearly two hours after a smaller 4.4-magnitude quake.

Among the dead were a pregnant woman and two children, said regional newspaper La Verdad. One woman lost her life when a modern three-storey building collapsed, it said.

A doctor said many people had been hurt.

"I had just finished attending to a patient. We all went out into the streets and had to treat people, some with serious inuries, many unconscious, because the ambulances could not reach them. They took more than 40 minutes," the doctor, identified only as Virtudes, told the online edition of El Pais.

"They just took away a man who had a wall fall on top of him."

New-born babies were evacuated from the town's Rafael Mendez hospital for fear it could collapse, the paper said. "The stairway was totally open. The roof of the building opposite and the medical centre fell off," one of the evacuated mothers told the paper.

Prime Minister Jose Luis Rodriguez Zapatero was informed of the disaster while he was in a meeting with King Juan Carlos, the premier's office said in a statement.

The king and prime minister then spoke to the president of the Murcia region and Zapatero immediately ordered the deployment of emergency military units to the area.

Earthquake damages were concentrated in the towns of Lorca and Totana, which lie in one of the most active seismic zones of the Iberian peninsula, but also spread as far as Albacete and Velez-Rubio in Almeria, the premier's office said.

Residents described confusion in the town of 92,700 inhabitants about 70 kilometres (45 miles) southeast of Murcia. Lorca traces its history back more than 2,000 years and boasts many medieval monuments.

"This is chaotic. All the ground is full of rubble," resident Jesus Ruiz told the paper.

"There are cracked buildings and all the ground is full of rubble and cornices. I saw them sewing up a child's head," said Ruiz, who was at work in an industrial zone when the quake struck.

Cristina Selva, 32, said she was playing with her two-year-old daughters. "The building moved and I was was very scared for the girls. I took them and the three of us got under the table to wait for it to pass," she said.

"It was the longest 20 seconds of my life."

It was the deadliest earthquake in Spain since April 19, 1956 when a tremor wrecked buildings and killed 11 people in Albolote, a town in the southern Spanish province of Granada.

Ironically, it struck on the same day many residents stayed away from work in the Italian capital Rome fearing a supposed prophecy of a devastating tremor by a self-taught Italian seismologist who died in 1979.