China has branded a landmark visit to Taiwan by US Speaker Nancy Pelosi as "extremely dangerous". It accused Pelosi, the most senior US politician in 25 years to visit the island China claims as its own, of "playing with fire". "Those who play with fire will perish by it," Beijing warned in a statement. Pelosi said her visit "honors America's unwavering commitment to supporting Taiwan's vibrant democracy" and did not contradict US policy. As her plane touched down, Chinese state media reported that its military jets were crossing the Taiwan Strait. Taiwan has denied any such action happened. It's night-time now in Taiwan, so plans are under way for what happens next in diplomatic moves on Wednesday. Pelosi will meet Taiwan's President Tsai Ing-wen in the morning, then fly out after lunch, the country's official central news agency said. The hope from Taiwan's presidential office is that the visit will deepen its partnership with the US, Reuters reports. It added the aim is to maintain peace and stability in the Indo-Pacific region. China's Foreign Affairs Ministry has strongly condemned Pelosi's visit, calling it a "serious violation of the One-China principle" that will have a "severe impact" on the political foundation of China-US relations. In a statement, the ministry said Pelosi's visit "seriously infringes upon China's sovereignty and territorial integrity". "It gravely undermines peace and stability across the Taiwan Strait, and sends a seriously wrong signal to the separatist forces for 'Taiwan independence'", the ministry said. China strongly urged the US to "stop playing the 'Taiwan card' and interfering in China's internal affairs", and to "not go further down the wrong and dangerous path". China — which sees Taiwan as a breakaway province which will one day reunite with it — has previously warned that its armed forces "will not stand idly by". In her statement, Pelosi said: "America's solidarity with the 23 million people of Taiwan is more important today than ever, as the world faces a choice between autocracy and democracy." In an article published in the Washington Post newspaper at the same time, Pelosi also wrote that Taiwan's "robust democracy... is under threat". "In the face of the Chinese Communist Party's (CCP) accelerating aggression, our congressional delegation's visit should be seen as an unequivocal statement that America stands with Taiwan, our democratic partner, as it defends itself and its freedom," she said. China has reacted furiously, vowing to conduct "targeted military exercises" in response. It also announced that the People's Liberation Army will conduct a series of live-fire military drills in the air and at sea around Taiwan later this week — warning ships and aircraft not to enter the affected areas. It follows days of escalating tensions ahead of the visit, in which Chinese warplanes had already ventured out as far as the median line, the unofficial dividing line separating China and Taiwan in the waters between them. However, while Pelosi's visit had been the subject of vast international speculation for days, it had been shrouded in secrecy up until the last minute. When she set off on a tour of Asia on Sunday, there was no mention of Taiwan on her official itinerary, which included Singapore, Malaysia, South Korea and Japan. The White House has been open in its opposition to any such trip, and President Joe Biden said the military assessed it as "not a good idea". China exerts international pressure on other nations to accept its "One China" policy — that there is only one Chinese nation, based in Beijing. Only 15 nations in the world have formal diplomatic relations with Taiwan. Long-standing US policy has been to recognize the Beijing government, but also maintain "robust unofficial" relations with Taiwan. That includes selling weapons for Taiwan to defend itself. As Speaker of the US House of Representatives, Pelosi is second in line for the US presidency after the vice-president. Yet she is also a long-standing critic of Beijing. As a congresswoman in 1991, two years after the Chinese government cracked down hard on protesters in Tiananmen Square, she visited the site of the demonstrations and unfurled a banner in memory of those who died — sparking an angry response from the government there. Pelosi is expected to stay overnight, Taiwanese media have reported, and meet members of the Legislative Yuan on Wednesday. — BBC