More than 100,000 protesters took to the streets of Taiwan's capital on Sunday as a two-week-long campaign against a trade pact with China gathered steam, piling further pressure on the island's leader.

The rally in Taipei - where many were dressed in black and some clutched sunflowers to symbolize hope - was one of the largest in recent years in Taiwan, an island that split from China over six decades ago after a civil war.

Protesters say the deal to open 80 of China's service sectors to Taiwan and 64 Taiwanese sectors to China was rushed through, and could leave Taiwan increasingly beholden to China's Communist Party leaders.

Some called for the resignation of Taiwan's China-friendly president Ma Ying-jeou, whose popularity has plunged despite helping to improve ties with China since taking office in 2008.

"We must safeguard our island's interests," said Chin Mei Ching, a 29-year-old mother who was pushing her one-year-old daughter in a buggy. "We have to guard against China using the economy to control us."

A coalition of student and civil groups behind the demonstration said that around 500,000 people had massed in streets near the Presidential Palace and the parliament building that has been occupied by protesters for nearly a fortnight.

Police put the figure at 116,000.

Police erected steel barricades to prevent protesters from reaching major government buildings including the cabinet offices that were raided by students last Sunday, sparking scuffles and the use of water cannon by police.

"We will not back down," Lin Fei Fan, one of the student leaders behind the occupation of Taiwan's legislature, told Reuters inside the building. "The large turnout today shows there is a clear majority in Taiwan that demands President Ma address our concerns in an acceptable manner."

Activists have plastered anti-Ma banners on the legislature walls, and stacks of armchairs block the exits.

ECONOMIC FOCUS

Ma has said the trade agreement is necessary for Taiwan's economic future, but opponents say the deal could hurt small Taiwanese companies. Many also worry the pact will allow Beijing to expand its influence over a fiercely independent and proudly democratic territory that China sees as a renegade province.

"Save Democracy, Don't Sell Our Country," read a banner on Sunday.

The trade pact was signed by China and Taiwan last June as a way to boost economic cooperation between the two sides but has yet to be formally ratified by Taiwan's legislature.

"China is using economic methods to invade Taiwan," said protester Liou Jong-yuan, a 47-year-old engineer.

The protest could strain the recent rapprochement between Taiwan and China, particularly if Ma capitulates on the trade deal that the protesters want scrapped.

Ma Ying-jeou said on Saturday the protests would not affect the potential for a meeting with Chinese President Xi Jinping. Both sides have expressed interest in a historic meeting between their leaders, though no timeframe or venue has been set.

Taiwan and China have been ruled separately since the Communists won China's civil war in 1949.