Taiwan Mainland Affairs Council Counselor Liang Wen-chieh said the increased warning against travel to China is also aimed at residents of the cities of Hong Kong and Macau, which are subject to China.

"If there is no need to go, then don't go", he said, noting that it is not a ban on visiting but is about protecting citizens and reminding them of the risk.

Beijing issued a statement last week threatening to execute "separatists" who support Taiwan's independence. China also promised to prosecute such people "wherever they are", despite the fact that China courts have no jurisdiction in Taiwan. Reuters therefore notes that "it is unclear how China can seek to enforce any court rulings outside its borders".

• On June 22, Taiwan's Ministry of National Defense said Taiwan's air defense systems detected 66 Chinese fighter jets around the island in the past 48 hours.