Taiwan's Defence Ministry said on Friday that it has scrambled fighter jets to monitor the activities of multiple Chinese air force jets that had crossed the midline of the Taiwan Strait and also into Taiwan's southwestern air defence identification zone.
Earlier this week, the US Department of State announced that it would be sending a senior diplomat, Keith Krach, to attend the memorial service for former Taiwanese political leader Lee Teng-hui. Washington and Taiwan have reportedly been in negotiations to initiate an economic dialogue.
Although officially the US follows the "One China" policy which does not recognise Taiwan as an independent entity, it also has trade and business ties with the island and supplies weapons there.
China sees Taiwan as a breakaway province which will eventually have to reunify with mainland China.