At least 248 people died when a powerful earthquake of magnitude 7.1 struck central Mexico on Tuesday, toppling buildings in the heavily populated capital where rescuers scoured frantically under the rubble of ruins for survivors.

Buildings that collapsed in the capital on Tuesday were apartment blocks, a school, a factory and a supermarket. The fashionable Roma district was hard hit, and a six-story apartment building was among several collapses reported.

Thousands ran into the streets in panic, and millions lost electricity when the quake struck around lunchtime. Hundreds of volunteers and rescue workers dug through the rubble with picks, shovels and their bare hands.

Mexico City Mayor Miguel Angel Mancera said 44 buildings were severely damaged or destroyed. Several major gas leaks and fires occurred.

Interior Secretary Miguel Angel Osorio Chong told local television rescue teams were working painstakingly with picks and shovels.

The United Nations expressed condolences and said it was ready to assist.