US House Speaker Nancy Pelosi said on Friday that China will not isolate Taiwan by preventing US officials from travelling there.

She made the remarks in Tokyo on the final leg of an Asia tour highlighted by a visit to Taiwan that infuriated China.

The Chinese have tried to isolate Taiwan, Pelosi said, including most recently by preventing it from joining the World Health Organisation.

"They may try to keep Taiwan from visiting or participating in other places, but they will not isolate Taiwan by preventing us to travel there," she said.

Pelosi said her trip to Taiwan was not intended to change the status quo for the island but to maintain peace in the Taiwan Strait. She also praised Taiwan's hard-fought democracy, including its progress in diversity and success in technology and business, and criticised China's violations of trade agreements, proliferation of weapons and human rights problems.

Pelosi, the first House speaker to visit Taiwan in 25 years, said on Wednesday in Taipei that the US commitment to democracy in the self-governing island and elsewhere remains ironclad .

Pelosi and five other members of Congress arrived in Tokyo late Thursday after visiting Singapore, Malaysia, Taiwan and South Korea.

China, which claims Taiwan and has threatened to annex it by force if necessary, called her visit to the island a provocation and on Thursday began military drills, including missile strike training, in six zones surrounding Taiwan, in what could be its biggest since the mid-1990s.

Earlier Friday, Japanese Prime Minister Fumio Kishida said that China's military exercises aimed at Taiwan represent a grave problem that threatens regional peace and security after five ballistic missiles launched as part of the drills landed in Japan's exclusive economic zone.

Kishida, speaking after breakfast with Pelosi and her congressional delegation, said the missile launches need to be stopped immediately.

In Taipei on Wednesday, Pelosi said the American commitment to democracy in Taiwan and elsewhere remains ironclad . She became the first House speaker to visit the island in 25 years.

Japanese Defence Minister Nobuo Kishi said five missiles landed on Thursday in Japan's exclusive economic zone off Hateruma, an island far south of Japan's main islands. He said Japan protested to China, saying the missiles threatened Japan's national security and the lives of the Japanese people, which we strongly condemn .

Japanese Foreign Minister Yoshimasa Hayashi, attending a regional meeting in Cambodia, said China's actions are severely impacting peace and stability in the region and the international community, and we demand the immediate suspension of the military exercises .

Japan has in recent years bolstered its defence capability and troop presence in southwestern Japan and remote islands, including Okinawa, which is about 700 km (420 miles) northeast of Taiwan. Many residents say they worry their island will be quickly embroiled in any Taiwan conflict. Okinawa is home to the majority of about 50,000 American troops based in Japan under a bilateral security pact.

At the breakfast earlier Friday, Pelosi and her congressional delegation also discussed their shared security concern over China, North Korea and Russia, and pledged their commitment to working toward peace and stability in Taiwan, Kishida said. Pelosi was also to hold talks with her Japanese counterpart, lower house Speaker Hiroyuki Hosoda.

Japan and its key ally, the US, have been pushing for new security and economic frameworks with other democracies in the Indo-Pacific region and Europe as a counter to China's growing influence amid rising tensions between Beijing and Taipei.

Days before Pelosi's Taiwan visit, a group of senior Japanese lawmakers, including former Defence Minister Shigeru Ishiba, visited the island and discussed regional security with Taiwanese President Tsai Ing-wen. Ishiba said Japan, while working with the United States to prevent conflict in the Indo-Pacific, wants a defence agreement with Taiwan.

On Thursday, the foreign ministers of the Group of Seven industrialised nations issued a statement saying there is no justification to use a visit as pretext for aggressive military activity in the Taiwan Strait . It said China's escalatory response risks increasing tensions and destabilising the region .

China cited its displeasure over the statement for the last-minute cancellation of talks between the Chinese and Japanese foreign ministers on the sidelines of the Association of Southeast Asian Nations meeting in Cambodia on Thursday.

Pelosi held talks on Thursday in South Korea, also a key US ally, which stayed away from the Taiwan issue, apparently to avoid upsetting China, focusing instead on North Korea's increasing nuclear threat.

In recent years, South Korea has been struggling to strike a balance between the United States and China as their rivalry has deepened.

The Chinese military exercises launched Thursday involve its navy, air force and other departments and are to last until Sunday. They include missile strikes on targets in the seas north and south of the island in an echo of the last major Chinese military drills in 1995 and 1996 aimed at intimidating Taiwan's leaders and voters.

Taiwan has put its military on alert and staged civil defence drills, while the US has numerous naval assets in the area.

China also flew war planes toward Taiwan and blocked imports of its citrus and fish.

China sees the island as a breakaway province and considers visits to Taiwan by foreign officials as recognising its sovereignty.

The Biden administration and Pelosi have said the United States remains committed to the so-called one-China policy, which recognises Beijing as the government of China but allows informal relations and defence ties with Taipei. The administration discouraged but did not prevent Pelosi from visiting.

Pelosi has been a long-time advocate of human rights in China. She, along with other lawmakers, visited Beijing's Tiananmen Square in 1991 to support democracy two years after a bloody military crackdown on protesters at the square.

As leader of the House of Representatives, Pelosi's trip has heightened US-China tensions more than visits by other members of Congress. The last House speaker to visit Taiwan was Newt Gingrich in 1997.

China and Taiwan, which split in 1949 after a civil war, have no official relations but multibillion-dollar business ties. (AP)