TAIPEI (AFP) - Taiwan has destroyed more than 100 birds smuggled from the mainland as the island steps up measures against the H7N9 avian flu virus that has killed seven people, officials said Tuesday.

The coastguard Monday seized 109 parrots and pigeons illegally transported from the mainland, arresting four male suspects in the fishing port of Nanliao in northern Hsinchu county.

"This is a sensitive moment. All the birds have been destroyed," coastguard official Kuo Sen-yao said.

Since China announced over a week ago that H7N9 avian influenza had been found in humans for the first time, the number of people infected has risen to 24, almost half in the eastern city of Shanghai, with seven deaths.

Taiwan has stepped up temperature checks at airports on passenger arrivals from Jiangsu, Anhui, Shanghai and Nanjing, where the infections have been reported.