As many as 154 Chinese passengers were on the flight that had taken off from Malaysian capital Kuala Lumpur early on Saturday and was scheduled to land in Beijing at 6.30 am (local time).
Till late evening, there was no trace of the Boeing B777-200 aircraft, now presumed to have crashed into the South China Sea soon after flying over the coast of Vietnam. The Malaysian air traffic control authorities lost communication with flight MH370 around 2.40am (local time) on Saturday.Read: China bound missing Malaysian flight presumed crashed; five Indians on board
Vietnam, however, said rescue planes searching for the missing jet spotted two large oil slicks in the sea and it was sending boats to the area.
"Two of our aircraft sighted two oil slicks around 15 to 20 kilometres long, running parallel, around 500 metres apart from each other," the army's deputy chief-of-staff, Vo Van Tuan, told state-run VTV.
A file photo of Malaysia Airline's ground staff parking a Boeing 777-200 at Kuala Lumpur International airport. (AFP photo)
The sighting of the oil slicks was the first possible sign that the missing Malaysia Airlines flight MH370, a twin-engine Boeing 777 jetliner, could have gone down in the waters between southern Vietnam and northern Malaysia.
Read: Vietnam mounts search for Malaysian airliner carrying 239
"We are not certain where these two oil slicks may have come from so we have sent Vietnamese ships to the area," said Tuan, speaking live on Vietnamese television.
The Malaysia Airlines said on its website that on board the aircraft were 12 crew members and 227 passengers, including 154 Chinese, an infant among them, and 38 Malaysians.
The five Indians, presumed dead, included a family of three travelling to Beijing.
A man takes pictures of a flight information board displaying the scheduled time of arrival of Malaysia Airlines flight MH370 (top, in red) at the Beijing Airport. (Reuters photo)
They were identified as Chetana Vinod Kolekar, 54, Swanand Vinod Kolekar, 22, Vinod Suresh Kolekar, 58, Chandrika Sharma, 50, and 43-year-old Shirsath Kranti Pralhad.
The Kolekars were coming to China to meet their Beijing-based son, Sanved.
It was learnt that, Sharma, a businesswoman from Chennai, was on her way to Mongolia from Beijing. Prahlad was coming to the Chinese capital to subsequently join her husband in North Korea.
Read: China sends two ships to help in rescue work for missing plane
State media reported that in the flight was a team of 24 Chinese calligraphers and painters returning to Beijing after attending an exhibition of their work in Kuala Lumpur.
The artists came from cities across China such as Beijing, Shanghai, Shandong, Jiangsu and Sichuan, the China Daily newspaper reported.
The newspaper's website said a third of the Chinese passengers on board the plane were aged 80 or above and about 20 were above 65.
In Beijing, tempers ran high with relatives of victims complaining that officials from the airlines did not share information in a timely manner.
A large number of relatives and family members rushed to the Beijing Capital International Airport soon after the news of the missing flight broke in the morning.
Many were already present at the airport to receive them when they heard that the flight had gone missing.
A crying woman is escorted to a bus for relatives at the Beijing Airport after news of the missing Malaysia Airlines Boeing 777-200 plane. AFP
Some broke down during their painful wait for news about their families and friends.
A hastily convened press conference by the airlines at city hotel lasted for about five minutes. Relatives complained that an airlines official simply read out from a statement that had already been posted on the airlines' website.
"Except reading out a piece of paper, the company has done nothing to comfort us or provide updates," a woman in her 30s told Xinhua news agency.
"There's no one from the company here, we can't find a single person. They've just shut us in this room and told us to wait," a middle-aged man, who declined to give his name, told Reuters news agency.
"We want someone to show their face. They haven't even given us the passenger list," he said.
Read: Chennai-based NGO activist among five on board missing Malaysia Airlines plane
A team of police personnel was posted around the hotel after grieving relatives also complained against media-persons who had descended on the hotel in huge numbers to track the developments and interview family members.
Earlier in the day, Chinese aviation authorities were informed by Vietnamese counterparts that Vietnam, Malaysia and Singapore are conducting a joint search south of Vietnam's Tho Chu Islands.
Malaysian transport minister Hishamuddin Hussein told a press conference in Kuala Lumpur his government had contacted the departments of maritime affairs of China, Vietnam, the Philippines and Indonesia to jointly search for the missing plane.
China has dispatched two maritime rescue ships to the South China Sea to help in rescue work.
President Xi Jinping directed the ministry of foreign affairs as well as Chinese embassies and consulates to strengthen contact with departments of the countries concerned and pay close attention to the search and rescue work for the flight.
"Premier Li Keqiang has instructed Chinese officials to intensify communication with Malaysian civil aviation agencies for better search and rescue efforts.
He also called for details of the Chinese passengers aboard the plane to be verified as soon as possible," Xinhua said.
Relevant departments should cooperate with foreign parties to prepare for emergency rescue and liaise with passengers' families in a timely and appropriate manner, Li said.
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(With inputs from AFP)