US House Speaker Nancy Pelosi has arrived in Taiwan. It's the first visit there by America's third highest-ranking official in 25 years. The veteran Democrat made the stop despite strong opposition from Beijing, which regards Taiwan as a breakaway province.

Pelosi's plane touched down in Taipei late on Tuesday night after spending several hours in Malaysia. Her official Asian tour itinerary also includes South Korea and Japan but not Taiwan.

She issued a statement saying the congressional delegation's visit to Taiwan honors America's unwavering commitment to supporting Taiwan's vibrant democracy.

But she also said her visit in no way contradicts longstanding US policy, and Washington continues to oppose unilateral efforts to change the status quo.

Local media say Pelosi is expected to meet President Tsai Ing-wen on Wednesday before flying out of Taiwan in the afternoon.

Officials in Beijing have repeatedly warned of resolute and strong measures to safeguard their country's sovereignty, should Pelosi insist on visiting Taiwan.

Chinese Foreign Ministry Spokesperson Hua Chunying said, "It's the US that is conducting provocative actions, and that has caused escalating tensions in the Taiwan Strait. So the US should bear all the consequences."

Beijing has also recently released a series of videos that appear to show the Chinese military in battle mode.

The footage also shows what experts say could be a new hypersonic missile system for targeting aircraft carriers.

But they are not the only ones on a higher state of alert. More than 20 aerial refueling aircraft have been deployed to a US military airbase in the southern Japanese prefecture of Okinawa.

NHK crew also spotted several F-15 fighter jets taking off, plus surveillance aircraft.