China's top negotiator with Taiwan began a visit Tuesday as activists protested against what they described as Beijing's attempt to annex the island by offering economic benefits.

Chen Deming, who was China's commerce minister from December 2007 to March 2013, was greeted by dozens of slogan-chanting protestors upon his arrival at Taoyuan airport in the north.

"I'm here for economic and trade fact-finding," he told reporters when asked he would push for Taiwan's parliament to approve a controversial services trade pact with China.

It was Chen's first visit to Taiwan since he was inaugurated in April as president of China's Association for Relations Across the Taiwan Straits, which handles exchanges with Taiwan in the absence of official contacts.

Taiwan's government has said the pact will benefit the economy, but it is strongly opposed by the opposition who fear it will hurt smaller service companies and cost many Taiwanese their jobs.

The pact is one of the follow-up agreements to a sweeping Economic Cooperation Framework Agreement signed in 2010 to reduce trade barriers between China and Taiwan.

Demonstrators chanted slogans and displayed signs reading "China, hands off Taiwan" and "Democracy and human rights not for sale".

The Taiwan Solidarity Union, a radical pro-independence party, has pledged to mobilise supporters to shadow Chen during his eight-day trip, but he said he was unworried by the prospect of unruly protests.

"I believe Taiwan people will provide me with necessary safety measures. Taiwan people are civilised," Chen said.

The China-sceptic Democratic Progressive Party, the main opposition party, has also demanded that Taiwan make representations to Chen over Beijing's controversial weekend declaration of an air force identification zone.

This zone includes islands disputed between China and Japan, which Taiwan also claims.

China still considers Taiwan part of its territory awaiting reunification, even though the two sides split back in 1949 at the end of a civil war.

But relations have warmed since Ma Ying-jeou of the China-friendly Kuomintang party came to power in 2008 on a platform of strengthening trade and tourism links. He was re-elected in January 2012.