China's countermeasures in response to United States House Speaker Nancy Pelosi's visit to Taiwan are necessary and legitimate, as they are taken to safeguard its sovereignty and territorial integrity as well as the principles governing international relations, officials and experts said.

State Councilor and Foreign Minister Wang Yi said on Thursday that if China does not resolutely resist the "manic, irresponsible and highly irrational" act of the US side, the principle of international relations on respecting sovereignty and territorial integrity will become empty words, separatists and extremists will become more rampant, and the region's hard-won peace and stability will be seriously jeopardized.

What China has done and will do are necessary and timely countermeasures that aim to warn against provocateurs and also protect regional stability and peace across the Taiwan Straits, he said.

China's countermeasures include staging military drills near Taiwan, conducting large-scale air and naval activities, punishing organizations related to die-hard "Taiwan independence" elements, and suspending natural sand exports to Taiwan, as well as the imports of some farm produce from the island.

Wang, who is attending the "ASEAN-plus" foreign ministers' meetings in Cambodia, canceled a scheduled meeting with Japanese Foreign Minister Hayashi Yoshimasa after Yoshimasa, with other foreign ministers of the Group of Seven nations and the high representative of the European Union, issued a joint statement about Taiwan.

The statement groundlessly accused China of escalating tensions across the Taiwan Straits.

Foreign Ministry spokeswoman Hua Chunying said at a regular news conference on Thursday that tensions across the Taiwan Straits are fundamentally caused by the US' connivance on Pelosi's visit to Taiwan by taking a military plane, disregarding China's strong opposition.

The Chinese government is justified and has the right to do whatever is necessary to respond to such a major incident, which substantially upgraded relations between the US and the Taiwan region in violation of the one-China principle, she said.

In a statement issued on Wednesday, the spokesperson for the Chinese Mission to the EU also refuted the joint statement, saying the smearing of China by foreign hostile forces and separatists in Taiwan cannot hide their sinister intention of separating Taiwan from the motherland.

The measures adopted by the Chinese government to safeguard sovereignty and territorial integrity are absolutely necessary and very appropriate, and they reflect the common aspirations of the more than 1.4 billion Chinese people, the spokesperson said.

Ma Xiaoguang, spokesman for the Taiwan Affairs Office of the State Council, said on Thursday that the measures China has taken to safeguard its sovereignty, security and development interests in accordance with international law and basic norms governing international relations are justified, legitimate and reasonable.

The international community has also voiced its support for the one-China principle following Pelosi's visit to Taiwan and for China to take all necessary measures to safeguard its sovereignty and territorial integrity.

United Nations Secretary-General Antonio Guterres reiterated the UN's support for the one-China principle on Wednesday. "We abide by General Assembly resolutions, by the one-China policy, and that is the orientation that we have in everything we do," he said.

In a joint statement published on Thursday, foreign ministers of the Association of Southeast Asian Nations who are meeting in Phnom Penh, Cambodia, also reiterated ASEAN member states' support for the one-China principle.

George Muntu, an analyst on international politics and foreign affairs based in Dar es Salaam, Tanzania, said that the US and the Democratic Progressive Party authorities in Taiwan have employed a salami-slicing tactic of pressing step by step in seeking the island's independence.

"It should be understood that China, as a sovereign state, has every reason to defend itself and protect its territories by any means. The international community should criticize Pelosi's provocative visit to Taiwan and urge the US to respect the one-China principle and stop interfering in China's internal affairs," he said.

Xu Bu, president of the China Institute of International Studies, said the US is seriously misleading the international community by falsely blaming China for changing the status quo across the Taiwan Straits.

The truth is that the DPP authority is trying to violate the one-China principle by soliciting US support, he said.

"The US should realize the severe harm of 'Taiwan independence', stop interfering in China's internal affairs and not go further on the wrong path," Xu said.