A powerful 6.5 magnitude earthquake shook Mexico on Saturday, killing at least two people, knocking out lights in parts of the capital and sending people rushing into the streets.

There were no immediate reports of severe damage or injuries in Mexico City but emergency services said an 18-year-old man was killed when a roof collapsed in Iguala, a small city between the capital and the tourist resort of Acapulco.

A 25-year-old man was killed when a rock fell on a small van on the Mexico City-Acapulco highway, a spokesman for emergency services in southwestern Guerrero state said.

I was dreadfully afraid, I thought it was never going to end, said Laura Gonzalez, who was drinking in a bar in the capital at the time of the quake, which lasted 40 seconds.

A severe earthquake in 1985 killed thousands of people and wrecked parts of Mexico City, and many residents live with the fear of a repeat.

I was on the fifth floor when I felt it. It was a very strong shake, said Amor Lajud. My dogs started barking. I just rushed for the exit and got out.

Lajud lives in an apartment building in the fashionable Condesa neighbourhood of Mexico City, which suffered serious damage in the 1985 quake.

Shoppers at a popular department store in Condesa rushed out to the street, some of them crying and shouting, and traffic lights were out at several intersections, causing traffic jams.

The epicentre of the quake was 28 miles (45 km) from Iguala in Guerrero and was 40 miles (64 km) deep, the U.S. Geological Survey reported. The quake, originally reported as 6.7 on the magnitude scale, was felt in other states including Michoacan, Puebla and Hidalgo, local media reported.

The most damage was in Iguala because the epicentre was very close to there, a spokesman for Guerrero emergency services said.

Landslides had closed highways in the Pacific coast state but the duty fire officer in Acapulco said that while residents of the port city felt the earthquake and telephone services were down, there were no reports of major damage.

Power was knocked out in many districts of the capital and one building was evacuated, but Mexico City Mayor Marcelo Ebrard said water services, the subway and the airport were working normally.

The city centre is fine, there are people skating on the ice rink, Mexico City emergency services spokesman Manuel Mondragon said of the winter entertainment facility set up in the central Zocalo square. At the moment, there is no reason for concern.

A source from phone operator Telcel said services went out briefly in some sections of the city as the mobile network was overloaded with people trying to call family and friends.

State oil monopoly Pemex, which has few installations on the Pacific coast, said there were no reports of damage.

(Additional reporting by Veronica Gomez, Luis Rojas and Mica Rosenberg; writing by Krista Hughes; Editing by Kieran Murray and Eric Walsh)