Beijing maintains that Taiwan is part of China's territory and will continue working towards reunification with the self-governed island through peaceful means, Chinese Premier Li Keqiang has said.

"We should promote the peaceful development of cross-Strait relations and advance the process of China's peaceful reunification," Li said in a report to some 3,000 delegates of the National People's Congress, which kicked off in Beijing on Sunday.

The government in Beijing remains committed to the "One China principle," which states that Taiwan is part of China, he reiterated.

The premier stressed the commitment of the Chinese authorities "to take resolute steps to oppose 'Taiwan independence'."

Taiwan's Mainland Affairs Council responded to Li's comments with a short statement, insisting that the island was not subordinate to Beijing, and urging China to "pragmatically handle cross-strait affairs with an attitude of rationality, equality and mutual respect."

Taiwan has been self-governed since 1949, but never officially declared independence from China. Beijing considers the island to be a part of its territory and strongly opposes its contacts with the US, which backs Taipei's push for sovereignty and sells state-of-the-art weapons to the government of President Tsai Ing-wen. Washington has also promised to defend Taiwan if China resorts to using force against it.