Two Taiwanese businesspeople based on the Chinese mainland were convicted and sentenced Wednesday after they were found guilty on charges of spying for the island's former rival China, a court said.

In an espionage case that has shocked military gurus, businesswoman Chou Yi-ru was sentenced to four years while businessman Chiang Fu-ming three years on charges of treason, the High Court in central Taiwan said in a statement.

Both of them, arrested in February, are allowed to appeal, it said.

The investigation into the case found that Chou joined the Chinese espionage service six years ago and recruited Chiang and also his nephew, a Taiwanese air force captain at a radar command and control centre, a year later.

The captain, also arrested in February on charges of leaking classified data to China, has been investigated separately by a military court.

The arrest of the captain has alarmed the authorities, given the sensitive position he had held.

Taiwan's defence ministry had declined to provide details of the espionage, but the widely-circulated Next Magazine had said the Chinese military has long sought access to the centre which houses highly sensitive information including details on the air force's "Strong Net" radar system.

The centre in the north is responsible for surveillance of the skies stretching from the island's north to southeastern Chinese coastal provinces like Fujian, Zhejiang and Jiangxi, according to the magazine.

The leaked data may allow China to obtain information regarding the US-made Patriot surface-to-air missiles that Taiwan has deployed, it said.

Chen Chen-hsiang, a former general who is now a legislator in the ruling Kuomintang party, had said he was "shocked" at the news as the unit was supposed to be highly confidential.

Ties between Taipei and Beijing have improved markedly since Ma Ying-jeou of the China-friendly Kuomintang party came to power in 2008 on a platform of beefing up trade and tourism links.

But the episode has highlighted Beijing's lingering hostilities towards the island, which it still regards as part of its territory awaiting to be reunified -- by force if necessary.

In July last year, a Taiwanese general lured by a honey trap into spying for China was sentenced to life in prison by a military high court, in one of the island's worst spying cases for half a century.

The island has governed itself for more than six decades since splitting from the mainland in 1949 at the end of a civil war.