Noted the following from Yahoo News Singapore
UPDATE [12:37]: Tuoi Tre, a leading daily in Vietnam, reports that the Vietnamese Navy has confirmed the plane crashed into the ocean. According to Navy Admiral Ngo Van Phat, Commander of the Region 5, military radar recorded that the plane crashed into the sea at a location 153 miles South of Phu Quoc island.
UPDATE [11:32am]: VN Express, Vietnam's largest news site, reports that Vietnam Emergency Rescue Center just announced it has found signal of the missing plane at 9.50am 120 miles South West of Ca Mau cape, the Southern-most point of Vietnam.
The signal is believed to be the ELT (Emergency Locator Transmittor) , which can be activated manually by the flight crew or automatically upon impact.