Protesters barricaded themselves inside Taiwan's parliament for a third straight day on Thursday, threatening "further action" if the government pushes ahead with its plans to ratify a contentious trade pact with China.

More than 200 protesters -- mostly young students -- stormed through security barriers and took over the parliament's main chamber late Tuesday in the first such occupation of the building in Taiwan's history.

Hundreds of police officers attempted to barge their way in on Wednesday and end the occupation, but they failed to breach the improvised barricades fashioned by the students out of piles of armchairs.

As the stand-off entered a third day, student leader Chen Wei-ting said the protesters would mount "further action" unless President Ma Ying-jeou responds to their demands by Friday.

"We demand the government return the pact to China, tell China we don't accept it," student leader Lin Fei-fan told reporters, whose antics have been broadcast around the clock by Taiwanese TV networks.

"We ask President Ma Ying-jeou to respond to our demands by noon Friday or we will take further action," Chen added, as the crowd chanted "return the service trade pact, defend democracy."

While waiting for the government's response in the chamber short of air conditioning, the protesters kept chanting slogans and singing as they managed to keep their spirits high.

Echoing the protestors' appeal, Taiwan's leading opposition Democratic Progressive Party (DPP) also warned of the Kuomintang government's any attempt to disperse the protest gathering by force.

"Or we would mobilise supporters to surround parliament," DPP Chairman Su Tseng-chang told reporters amid rumours that the government could use police to quash some local media have termed as Taiwan's version of "Jasmine Revolution".

Su, a former premier while the DPP was in office for eight years to 2008, hailed the students as "democracy guardians" while condemning Ma for his undaunted efforts to push parliament to ratify the controversial agreement.

The president's office declined to comment on the demands, saying only that it supports the parliament's efforts to "properly handle the situation in accordance with the law".

The protesters have vowed to occupy the parliament until Friday, when lawmakers are set to hold a full session to review the pact.

Signed in July, the agreement is designed further to open up trade in services between China and Taiwan, which split 65 years ago after a civil war.

Like the protesters, the DPP says the deal will damage Taiwan's economy and leave it vulnerable to political pressure from China.

"We've never opposed the service trade agreement. But it must be signed (under the principles of) fairness and equality, equal opening to each other, fair competition, taking care of people's livelihood as well as maintenance of national security," Su said.

His remarks underscored the lingering threats from the giant neighbour despite the fast warming ties as a result of the China detente initiated by Ma since 2008.

The protesters say the deal will damage Taiwan's economy and leave it vulnerable to political pressure from China.

Taipei's police force has deployed some 2,000 officers to the parliament, who are guarding it in shifts as around a thousand more protesters remain in its grounds.

Police said 38 officers received mild injuries attempting to force their way back into the chamber on Wednesday.

Parliament speaker Wang Jin-pyng on Thursday pledged to resolve the situation with "appropriate methods".

The Kuomintang government has said the agreement is a litmus to Taiwan's resolve to open its markets, warning that failure to ratify the agreement would be a grave setback in the efforts to seek more free trade agreements by the trade-reliant island.

The pact passed its first parliamentary hurdle on Monday after it was approved by a committee in spite of opposition from some lawmakers.

The approval -- the first of three ratifications needed to pass the bill -- sparked a brawl between rival lawmakers and prompted three legislators from the opposition Democratic Progressive Party (DDP) to announce a 70-hour hunger strike.

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

Ma has overseen a marked thaw in relations with China since he came to power in 2008, pledging to strengthen trade and tourism links.

China has emerged as the island's leading trade partner, while dozens of agreements between the two have been signed.

But China still considers Taiwan as part of its territory awaiting reunification -- by force if necessary.