TAIPEI, Sept 13 (Reuters) - Taiwan's defence ministry said it spotted 28 Chinese air force planes in its air defence zone on Wednesday morning, part of what Taipei calls regular harassment by Beijing.

Democratically-governed Taiwan, which China views as its own territory, has complained in recent years of stepped up Chinese military activities near the island as Beijing seeks to assert its sovereignty claims.

Taiwan's defence ministry said that beginning at around 6 a.m. (2200 GMT Tuesday) Chinese war planes, including J-10 fighters, had flown into the southwestern corner of the island's air defence identification zone, or ADIZ.

Some of the Chinese aircraft crossed the Bashi Channel to carry out drills with the Chinese aircraft carrier the Shandong in the Pacific, the ministry added.

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

A Chinese naval formation led by the Shandong entered the western Pacific for training, Taiwan's defence ministry said on Monday.