ISTANBUL

Amid heightened tensions over a possible trip by US House Speaker Nancy Pelosi to Taiwan, incidents of an alleged bomb threat and cyberattack were reported Tuesday on the self-ruled island. 

Taiwan Aviation Police Bureau said that security was beefed up at Taoyuan International Airport "after it received a bomb threat," official Focus Taiwan reported.

The bureau said it had received reports of "three explosive devices would be placed in the airport," but "nothing suspicious has been found on the premises" so far.

This comes as Pelosi is expected on the island, home to over 24 million people, on Tuesday night.

Her plane is expected to land at Taipei Songshan Airport around 10.20 p.m. local time (1420GMT).

It has triggered angry reaction from China which considers Taiwan as its "breakaway province," while Taipei has insisted on its independence since 1949.

Taiwanese presidential office also has the reported cyberattack on its website, which was down for around 20 minutes.

Calling Pelosi's possible trip as violation of China's territorial integrity, Beijing has warned the US of consequences with its responsibility on Washington. 

There is heightened military activity in and around Taiwan with the US dispatching four warships, while China is mobilizing its naval, air and land forces close to the island.

Taiwan has also put is military on alert, while China has rescheduled flights to Fujian, the closest province to Taiwan in southern China.

Beijing has expanded its trade blacklist on food imports from Taiwan which is seen as a consequence of Pelosi's possible trip to the island.

Pelosi is on an official trip to Asia with stopovers in Singapore, Malaysia, Japan, and South Korea, without any official mention of Taiwan.

At least two five-star hotels have been booked in Taipei for the stay of the visiting US delegation of lawmakers.

Pelosi, who will be the first US House speaker to visit Taiwan in 25 years, is expected to meet Taiwanese President Tsai Ing-wen before engaging with Taiwanese lawmakers.

While Taiwanese officials are mum on the visit, China, which claims the self-governing island as a part of its territory, has said its military "won't sit by idly" if its "sovereignty and territorial integrity" is being threatened. It has held several military drills near Taiwan since the speculations on the visit.

Quoting experts, state-run Chinese daily Global Times reported: "The entire security mechanism of Taiwan island will be considered when Beijing reacts to Pelosi's visit. The Chinese mainland may start to execute control of the airspace and waters adjacent to the island to ensure there is not a second Pelosi visit to the island." 

Last week, China's President Xi Jinping told his US counterpart Joe Biden "not to play with fire" over Taiwan.