A powerful earthquake rocked a broad belt of central Mexico today, killing at least 15 people, injuring hundreds of others and damaging the graceful colonial heart of the city of Puebla, officials and news reports said.

The tremor, which struck at 3:41 p.m. local time (4:41 p.m. EDT) and lasted more than 40 seconds, was a magnitude 6.7 on the Richter scale, the National Seismological Service reported. It caused panic across a wide swath of the country, shaking office buildings in Mexico City, shattering school windows in southern Oaxaca state and rattling high-rise hotels in Acapulco.

The epicenter was in Huajuapan de Leon in Oaxaca, about 140 miles southeast of Mexico City, but the worst damage occurred in neighboring Puebla state.

Puebla's interior minister Carlos Alberto Julian said 11 people had been confirmed dead in his state. In the southern state of Guerrero, a woman died from a heart attack, and in the Gulf coast state of Veracruz, a farm laborer died in a landslide, officials said.

In Mexico City, two people died of heart attacks caused by shock due to the quake, the interior ministry said.

In Puebla, the earthquake cracked walls and floors in the city center, which is filled with elegant churches and homes decorated with colorful tiles. Fragile balconies crashed to the ground.

Among the worst-hit buildings was Puebla's turn-of-the-century city hall, where several employees were trapped in rubble.

"The city hall is severely damaged. We are awaiting more rescue workers," Puebla mayor Mario Marin told Radio Red about three hours after the quake.

President Ernesto Zedillo declared Puebla state a disaster area and mobilized soldiers to help in the relief effort. He cut short a trip to the Caribbean resort of Cancun and traveled to Puebla to inspect the damage.

"The first thing we have to lament is the loss of human life," Zedillo said after surveying city late today. He pledged federal authorities would immediately seek ways to restore the historic center of the state capital. "We can't allow the loss of this extremely important patrimony," Zedillo said.

Television footage showed workers picking through waist-high rubble in the 17th-century church of San Agustin in central Puebla.

Alejandro Soto, director of the Puebla city Red Cross, said about 200 people in the city of 1.2 million suffered at least minor injuries, with 10 seriously hurt. The government's Notimex news agency reported that thousands of people in various cities were treated for panic attacks.

In the Mexican capital, tens of thousands of people fled into the streets as tall buildings seemed to roll like ships at sea and officials were inspecting hundreds of structures for possible damage.

"I felt dizzy and I saw that all the lamps were swinging," said Mary Cervantes, a 52-year-old housewife. "I went running for the door."

Streets in Mexico City were crowded with people fearful of returning to buildings.

Mexico's largest recent earthquake, on Sept. 19, 1985, was recorded at magnitude 8.1 and killed at least 9,500 people.

Robert Meli, director of the National Center for Disaster Prevention, told local TV Azteca that today's quake was "between five and 10 times smaller than the one in 1985."

CAPTION: Rescue workers remove debris from an apartment demolished by an earthquake in downtown Puebla. The quake registered 6.7 on the Richter scale, Mexican officials said.