The Chinese government, meanwhile, demanded that Malaysia turn over the satellite data it used to conclude that Malaysia Airlines Flight 370 was lost in the southern Indian Ocean with no survivors during a flight to Beijing.
Among the flight's 239 passengers, 153 were Chinese nationals, making the incident a highly emotional one for Beijing, and the government's demand reflected the desire among many Chinese relatives of passengers for more conclusive information on the plane's fate.
Nearly 100 relatives and their supporters marched to the embassy in the late morning, wearing white T-shirts that read "Let's pray for MH370'' as they held banners and chanted.
"Tell the truth! Return our relatives!'' they shouted. There was a heavy police presence at the embassy when the group arrived, and journalists were being kept away.
Family members of the missing passengers have complained bitterly about a lack of reliable information. Many have said they suspect they are not being told the whole truth _ a not-uncommon mindset among ordinary Chinese accustomed to dealing with their own opaque and single-party communist state.
Deputy Foreign Minister Xie Hangsheng told Malaysia's ambassador to Beijing that China wanted to know what exactly led Malaysia to announce Monday night that the plane had been lost, China's Foreign Ministry said on its website Tuesday.
"We demand the Malaysian side to make clear the specific basis on which they come to this judgment,'' Xie was quoted as telling Datuk Iskandar Bin Sarudin.
There was no immediate response from the Malaysian side. Flight 370 vanished less than an hour into an overnight flight March 8 from Kuala Lumpur to Beijing.
Monday's announcement that a thorough analysis of satellite data no longer left any reasonable doubt that the plane went down in the Indian Ocean sparked mournful, angry and chaotic scenes at the Beijing hotel where many relatives had gathered.
Around 2:00 a.m. Tuesday morning (1800 GMT Monday) a group of family members read out a statement condemning Malaysia Airlines and the Malaysian government and military and vowing to hold them responsible for the deaths of their loved ones.