TAIPEI, March 1 (Reuters) - Taiwan's defence ministry said on Wednesday it had spotted 19 Chinese air force planes in its air defence zone in the past 24 hours, part of what Taipei calls regular harassment by Beijing.

Taiwan, which China views as its own territory, has complained for the past three years or so of stepped up Chinese military activities near the island as Beijing seeks to assert its sovereignty claims.

China has said its activities in the area are justified as it seeks to defend its territorial integrity and to warn the United States against "colluding" with Taiwan, despite the anger this causes in Taipei.

Taiwan's defence ministry said 19 J-10 fighters had flown into the southwestern corner of the island's air defence identification zone, or ADIZ, though closer to the Chinese coast than Taiwan's according to a map the ministry released.

Taiwan's forces monitored the situation, including sending up its own air force planes, the ministry added, using the normal phrasing for its response to such Chinese incursions.

However, the aircraft did not cross the sensitive median line of the Taiwan Strait, which previously served as an unofficial barrier between the two sides but which China's air force has been flying over on an almost daily basis since staging war games near Taiwan last August.

No shots have been fired and the Chinese aircraft have been flying in Taiwan's ADIZ, not in its territorial air space.

The ADIZ is a broader area Taiwan monitors and patrols that acts to give it more time to respond to any threats.

The democratically elected Taiwanese government has repeatedly offered talks with China, but says the island will defend itself if attacked and that only the Taiwanese people can decide their own future.