Beijing on Monday blamed Kuala Lumpur for a lack of information about a vanished Malaysia Airlines flight, as tearful relatives of the 153 Chinese passengers aboard voiced frustration with all sides of the response effort.
Nearly two-thirds of the 239 people aboard Malaysia Airlines (MAS) flight MH370 were from China, and if the loss of the aircraft is confirmed, it would be China's second-worst air disaster in history.
"The Malaysian side attaches importance to the incident with a sincere attitude, but in light of the situation, the Malaysian side needs to step up their efforts," Chinese foreign ministry spokesman Qin Gang told reporters at a regular briefing.
Qin declined to pinpoint any specific areas of the Malaysian response with which Chinese authorities were dissatisfied, noting that "the incident is still under investigation".
But China's state-run media minced no words on Monday, lashing out at Malaysia and its national carrier over their handling of the missing jet, demanding answers despite the early stage of the investigation and calling for a swifter effort.
Officials said two Europeans whose names were on the passenger manifest -- who both had their passports stolen in Thailand -- were not on board.
"The Malaysian side cannot shirk its responsibilities," the Global Times newspaper, which is close to China's ruling Communist Party, wrote in a scathing editorial. "The initial response from Malaysia was not swift enough.
"There are loopholes in the work of Malaysia Airlines and security authorities," it said.
"If it is due to a deadly mechanical breakdown or pilot error, then Malaysia Airlines should take the blame. If this is a terrorist attack, then the security check at the Kuala Lumpur airport and on the flight is questionable."
China itself regularly enforces heavyweight security, while authorities are often secretive about real or alleged incidents.
The China Daily newspaper wrote in an editorial that "terrorism cannot be ruled out", with Malaysian and international authorities still at a loss to explain how at least two passengers were able to board with stolen Italian and Austrian passports.
"Who were they and why were they using false passports?" the paper asked.
"The fact that some of the passengers on board were travelling with false passports should serve as a reminder to the whole world that security can never be too tight, at airports in particular, since terrorism, the evil of the world, is still trying to stain human civilisation with the blood of innocent lives," it added.
Malaysia's police chief said Monday that one of the men who used the passports had been identified, after ministers reportedly said they had Asian facial features.
At a Beijing hotel, Malaysian embassy officials were processing visa applications for families wanting to take up an airline's offer to travel to Kuala Lumpur to be closer to the rescue operations.
Scores of relatives made their way into the room, some in groups of five or six, clutching handkerchiefs and wiping away tears from their faces.
Some family members are expected to travel from Beijing to Kuala Lumpur on a 1:30 a.m. flight Tuesday, but many said they would not go.
"There is more we can do here in China," one woman told AFP. "They haven't even found the plane yet."
Some have criticised Malaysia Airlines' response and information disclosure, asking the Chinese government to devote "strong attention" to the incident.
"There is very little information coming from the airline," lamented one 40-year-old Chinese man, who said his best friend was on the plane. "They are very slow. We have to rely on the media."
Others have called for top Chinese officials to help the family members deal with the airline, drawing a contrast with Malaysian Prime Minister Najib Razak, who has reportedly visited families in Kuala Lumpur along with his wife.
Beijing sent a working group to Malaysia Monday, the state-run Xinhua news agency said, including officials from the foreign, public security and transport ministries.
The aircraft's disappearance came one week after a deadly attack at a train station in the southwestern Chinese city of Kunming, in which a group of knife-wielding assailants killed 29 people and wounded 143.
Both Beijing and Washington have condemned the mass stabbing as an act of terror, with Chinese authorities blaming it on separatists from the restive far western region of Xinjiang.
Even as information remains sparse and the hours tick by, many relatives in Beijing continue to believe that the passengers may yet be found, according to one US-trained psychologist who counselled about 20 families awaiting news at the hotel.
"I think most of them are holding onto that thin ray of hope," he said. "Whether they believe it to be realistic or not, most of them are not letting it go."