Beijing also ruled out involvement of its nationals on board the aircraft carrying 239 people in any hijack attempt.
China has started searching its own territory along the northern corridor to trace the missing Malaysia Airlines flight MH370, China's Ambassador to Malaysia Huang Huikang said in Kuala Lumpur.
The search began after India, Pakistan and several other countries in the region denied that the plane might have flown over their territories towards Kazakhstan and Turkmenistan.
Based on latest information, the new search areas encompass a northern corridor stretching approximately from the border of Kazakhstan and Turkmenistan to northern Thailand, as well as a southern one from Indonesia to the southern Indian Ocean.
China said it was extremely concerned over the missing plane as 154 of the passengers are its nationals.
On its part, Malaysia maintained that the disappearance of its plane was a deliberate act.
Fresh reports surfaced that the flight's planned path was altered through a computer system in the cockpit.
With no definitive clue yet in one of the most puzzling aviation mysteries, Malaysia's Defence and Transport Minister Hishammuddin Hussein told reporters that the search area now covers a vast area of 2.24 million square nautical miles (7.7 million square kilometres).
The focus is now on huge areas over central Asia and Indian Ocean, territory size slightly larger than Australia, he said on the search operations for the missing Beijing-bound Boeing 777-200 Malaysia Airlines flight.
Twenty-six counties are assisting in the search operations.
In Beijing, Foreign Ministry spokesperson Hong Lei told reporters that China has deployed 21 satellites for the search operations.
"In accordance with Malaysia's request, we are mobilising satellites and radar to search over the Chinese section of the northern corridor which the Malaysian say the plane may have flown over," the spokesperson said.
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