CHONGQING, Aug. 20 (Xinhua) -- Yangtze River's water level in Chongqing Municipality exceeded historical high earlier Thursday morning, posing unprecedented threat to the metropolis in southwest China.

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At around 8 a.m. Thursday, the water level at the Cuntan hydrologic station in Chongqing reached 191.55 meters, 0.14 meters higher than the record in 1981, and was rising.

Chongqing, located in the upper reaches of China's biggest river, upgraded its flood-control response to Level-I on Tuesday, the highest rung in the four-tier emergency response system for floods.

At least 250,000 residents of Chongqing have been relocated to safe places.