"Some Chinese families, internet users and well-known people have aired some radical views," China's ambassador to Malaysia Huang Huikang said.
"These radical and irresponsible opinions do not represent the views of Chinese people and the Chinese government," Huang was quoted as saying by Hong Kong-based South China Morning Post.
Huang also defended Malaysian Prime Minister Najib Razak's use of the word "ended" - when describing the probability that the jet plunged into the ocean on March 8 - a phrase that infuriated relatives who said there was no evidence of a crash.
The relatives of 153 Chinese passengers aboard MH370 off late have criticised search missions. Some accused Malaysia of "murdering" loved ones by delaying the rescue mission, while others called for a boycott of Malaysian travel and goods.
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"None of the accusations are true," Huang said.
Earlier, state-run China Daily called on the relatives not to let anger prevail over facts and rationality, and prepare for funerals of their kin.
"Today no matter how distressed we are and how many details that are not clear, it is certain that flight MH370 crashed in the Indian Ocean and no one on board survived," an article in the daily said.
"Our hearts have turned cold," said one relative.
The Chinese protests and constant criticism had riled public opinion in Malaysia.
"If China is so good, why don't they just take over and find the plane," the Post quoted a senior Malaysian citizen as saying.
"Malaysian citizens, media and government officials have quietly seethed, and have heard enough. They want an end to what they see as a vulgar display of superiority and an overreaction by the Chinese over the missing airliner," the report in the Post said.
"But marching to the Malaysian embassy was the turning point. It's hypocrisy. The Chinese won't dare do anything like this against their own government, which is one of the most opaque in the world," he said.