Beijing, Jul 23 (IANS): The death toll in the 6.6-magnitude earthquake that hit northwest China's Gansu province has climbed to 89, officials said.

Till 6 p.m. Monday, 87 people in Dingxi city and two in the neighbouring city of Longnan were confirmed killed in the quake that jolted the border of Minxian and Zhangxian counties, Xinhua reported the Dingxi municipal government as saying.

Minxian reported the bulk of the casualties, with 87 deaths, five missing and 515 injured.

Till Monday evening, 422 aftershocks were recorded in the quake-hit region, with the strongest measuring 5.6 in magnitude, an official said.

The quake caused the collapse of more than 1,200 houses and severely damaged another 21,000 homes, he said.

Two helicopters and about 3,000 policemen, firefighters, local militiamen and government staff have been sent to the quake-hit region to help in rescue efforts.

The earthquake occurred in a fault zone that has seen 25 earthquakes with a magnitude of 5.0 or greater throughout history, the China Earthquake Administration said.

The strongest quake recorded in the fault zone had a magnitude of 8.0 and occurred July 21, 1654. That quake happened about 121 km from the site of the latest quake, the administration said.

Zhu Wenqing, a 40-year-old farmer, said his house survived the initial quake but eventually collapsed following seven or eight aftershocks.

Villagers said the victims were mainly elderly and children.

In Yongguang village, the quake caused a landslide that buried 12 residents.

Two bodies were found and one person was pulled out alive, but rescue efforts have been slow due to lack of heavy digging machinery, rescuers said.

Chu Xiaoyi, a 20-year-old villager, said the landslide destroyed his house. His family of three narrowly escaped.

"We were sleeping when it happened, so we ran out almost naked. Now we have nothing left and even our clothes are borrowed from neighbours," Chu told Xinhua.

Many people said they were concerned about the lack of food, shelter, electricity and unstable mobile phone signals after the quake damaged the infrastructure.

Communication in many villages has been cut off.