NEW : Chanthu has slowed but is moving steadily closer to southern China . NEW : Tropical storm could deluge already soaked areas with several inches of rain . NEW : State Council declares flood ` ` grave '' NEW : Xinhua also said the Qiongzhou Strait between the Chinese mainland and Hainan island was closed Wednesday as Chanthu headed toward south China . Chinese news agency says more than 700 deaths by flood this year .
NEW : Chanthu has slowed but is moving steadily closer to southern China . NEW : Tropical storm could deluge already soaked areas with several inches of rain . NEW : State Council declares flood ` ` grave '' NEW : Chinese news agency says more than 700 deaths by flood this year .