China is sending a special envoy to Malaysia to liaise with search and rescue operations for the missing Malaysia Airlines jetliner.

The move comes as families of the passengers who were aboard the Boeing 777-200 demanded further explanations from Kuala Lumpur.

A sign reading, "Son, Papa's and Mama's hewarts are broken; please come back" marks a protest at the Malaysian Embassy in Beijing on Tuesday. Feng yongbin / china daily

President Xi Jinping, attending the third Nuclear Security Summit in The Hague, instructed Vice-Foreign Minister Zhang Yesui to leave for Malaysia as soon as possible.

Xi has been closely following the search and rescue mission for the ill-fated flight MH370, which disappeared early on March 8 on a flight from Kuala Lumpur to Beijing with 239 people on board, including 154 Chinese nationals.

Premier Li Keqiang said on Tuesday that the search and rescue effort is still the top priority and urged Malaysia to provide more accurate and detailed information.

Two Chinese expert teams are already in Kuala Lumpur.

The General Office of the State Council has promised to continue to provide passengers' family members with medical treatment, psychological counseling and legal assistance.

Malaysian Prime Minister Najib Razak said on Monday night that based on analysis of satellite data the plane crashed into the southern Indian Ocean and there were no survivors.

Sleepless night

About 300 of the passengers' family members and supporters took to the streets in Beijing on Tuesday after a sleepless night following the Malaysian announcement.

They gathered at the Lido Hotel at 10 am to demand an explanation from the Malaysian government.

After no Malaysian official showed up, they boarded buses to the Malaysian embassy to petition for "a true answer".

Wearing white T-shirts bearing the words "Let's pray for MH370", the protesters held banners and chanted for about three hours. "Tell the truth. Return our relatives," they shouted.

Shi Xianwu, 23, whose older brother was aboard the plane, said: "The family members were angry at the crash announcement on Monday night, when no solid evidence and debris from the plane were found. My father and sister-in-law also joined the protest, and we are not going to leave until a final explanation is given."

Police standing in two lines cordoned off the embassy while the families tried to get through. Some protesters threw bottled water at the building.

The group presented a protest letter to the embassy before leaving in buses.