The Chinese ATC revelation, which appeared in a story posted by state news agency Xinhua, is not surprising given that contact with flight MH370 was lost two hours into the six hour flight.
An aircraft travelling on the KL-Beijing route would reach the southern Chinese coast roughly three hours into the six hour flight.
According to route data on flight tracking web site Flightaware, MH370 would have departed KL, flown northeast across the Malaysian peninsula, whence it would have crossed the South China Sea, making landfall in Vietnam.
The aircraft would have crossed the Mekong Delta region, and left the Vietnam coastline in the region of the central Vietnamese city of Da Nang.
By this point the aircraft would have been about two hours into the flight – roughly where contact was lost. After this, the aircraft would have passed to the South of Hainan Island, before reaching the coast of southern China.
A previous Xinhua report said that the search and rescue assets of Malaysia, Vietnam, and China had been activated.