A time bomb exploded Wednesday on a crowded tourist train bound for the majestic Inca ruins at Machu Picchu, killing seven people and wounding at least 38, authorities said.
An unidentified American was among the dead, and at least six Americans were reported wounded, a U.S. Embassy spokesman said.
Police said 28 people were wounded, but the railway company put the number at 38 or more. The names of the dead were not made public.
Six suspects were arrested, authorities said.
No group claimed responsibility for the bombing, but police have blamed Sendero Luminoso (Shining Path) guerrillas for a wave of recent attacks. Sendero Luminoso is a Maoist group that has been fighting the government for six years.
An estimated 250 imprisoned Sendero Luminoso guerrillas were killed June 18 when thousands of troops stormed three Lima prisons to put down uprisings by guerrilla inmates. Insurgents have made numerous attacks in Lima since the prison uprisings were crushed.
On Tuesday, President Alan Garcia ordered the arrest of 95 soldiers he said had killed 30 to 40 of the rebel inmates after they surrendered.
The explosion Wednesday ripped through the third car of a four-car tourist train as it was preparing to leave for Machu Picchu from Cuzco, said Jorge Nicholson, administrator of the state train system office in Cuzco.
The blast was caused by dynamite placed in an inside luggage rack, Nicholson said. The explosion knocked a hole in the wall and roof of the car, which was carrying 60 passengers, he said.
He said the dead were an American, two West Germans, a Brazilian, a Peruvian, a Spaniard and a person believed to be a foreigner but whose nationality was not known.
Three Americans who were hospitalized at Cuzco's Regional Hospital were identified only as Dr. Donald Mason of California, Sam Baker and Monica Rodriguez Acosta, who is in a coma.
Emma Zamalloa, an assistant to the station manager in Cuzco, said that the time bomb exploded just before the train was to depart for Machu Picchu, the Inca ruins in the Andes 70 miles north of Cuzco.
Zamalloa said the wounded were being treated at a hospital, and some were in serious condition.
Cuzco, former capital of the Inca empire, is a colonial city of cobblestone streets and red tile roofs 375 miles southeast of Lima. Cuzco and Machu Picchu are Peru's main tourist attractions.
The bombing Wednesday followed an order by Garcia for the jailing of police officers accused of slaying some of the rebel inmates after they had surrendered.
Garcia went on nationwide television Tuesday night and announced he could not keep silent about the police action and was ordering the arrests of those who "proceeded to brutally annihilate" up to 40 inmates who surrendered at San Pedro prison.
Fifteen of the 95 officers to be tried are higher-ranking officials of the police force that crushed the uprising of rebel inmates at San Pedro, the government newspaper La Cronica said.
The newspaper did not print the names of the police officers or describe their role in the killings.