BEIJING, Oct. 3 (Xinhua) -- China's national observatory on Wednesday issued a blue alert for Typhoon Kong-rey, which is expected to unleash gales and downpours in eastern regions.

The eye of Kong-rey, this year's 25th typhoon, was located on the Pacific Ocean about 570 kilometers southeast of Naha, Okinawa of Japan, as of 5 p.m. Wednesday, the National Meteorological Center (NMC) said.

It will continue to move northwest at a maximum speed of 20 km per hour and likely dwindle as it approaches the East China Sea, the NMC said.

Regions including Fujian, Zhejiang and Taiwan will be hit by gales on Wednesday and Thursday under the influence of Kong-rey and cold air.

China has a four-tier color-coded weather warning system for severe weather, with red the most serious, followed by orange, yellow and blue.

The NMC advised residents to stay indoors and boats to return to harbor, and warned of flash floods in mountainous areas.