China and Taiwan signed a landmark investment pact on Thursday as hundreds of protesters voiced their anger over the island's ever-closer economic ties with its giant former foe.

China's chief negotiator Chen Yunlin and his Taiwanese counterpart Chiang Pin-kung put their names to the long-awaited deal, which will provide a legal umbrella for Taiwanese companies operating in China.

"It's extremely important not only for Taiwan's investment and trade links with the mainland, but also for bilateral ties as a whole," Chiang told reporters after signing the agreement.

"It will also provide different ways to protect Taiwan's business interests in the mainland when disputes take place."

The agreement includes safeguards against sudden expropriation of property and also gives individual investors some protection in the case of legal problems with authorities.

Chen and Chiang also signed a cooperation pact to speed up customs procedures in the hope of boosting two-way trade.

The two deals follow the sweeping 2010 Economic Cooperation Framework Agreement (ECFA) that eased tariff restrictions and gave trade a major push.

But those who oppose closer ties with China fear the pacts will strengthen Beijing's hold over the island. Protesters have been tailing Chen since his arrival on Wednesday.

Police estimated close to 700 gathered in the streets of Taipei, including several hundred members of the Falungong spiritual movement, which has been banned in China for more than 12 years.

About 1,300 police officers were posted around the meeting venue, a landmark hotel on a hill overlooking Taipei.

Barbed wire was rolled out and police prevented a small truck covered in anti-China banners from approaching the building.

"I oppose the deals because China is trying to control Taiwan's economy so it can rule Taiwan," said protester Chen Che, demonstrating with about 50 others at a museum several hundred metres from the hotel.

"The deals have political purposes and they are steps towards unification. I'm worried about Taiwan's future if the government sells out to China like this. Without democracy we have nothing."

A spokeswoman for the pro-independence Taiwan Solidarity Union party said earlier this week that China had not respected any of the pacts it had signed so far and questioned why more agreements were being made.

Taiwan and China split in 1949 at the end of a civil war and remained implacable enemies for decades, even after the island's businesses started exploring opportunities across the strait.

Ties have improved markedly since Ma Ying-jeou became Taiwan's president in 2008 on a Beijing-friendly platform, leading to the signing of 18 agreements, including Thursday's, between the two sides to boost trade and civil exchanges.

China is Taiwan's largest trade partner and more than 80,000 Taiwanese companies now operate on the mainland, where they have invested more than $100 billion over the years.

It is the eighth time in four years that Chen and Chiang have met for talks that would have been unthinkable a decade ago but have now become almost routine.

Thursday's meeting could be their last, with observers expecting the 70-year-old Chen to retire after a change of leadership in Beijing this year and next.