The Philippines' foreign minister on Thursday slammed China's attempts to build islands in the disputed South China Sea, prompting Beijing to accuse Manila of making "trouble out of nothing".

Albert del Rosario repeated a warning that Beijing was reclaiming land around isolated reefs in the South China Sea to turn them into islands which could hold fortified positions or even airstrips.

The Philippine foreign secretary said the Chinese actions in the Spratly islands would impact freedom to navigate the strategic mineral-rich waters, through which large volumes of the world's trade pass.

"I will re-emphasise this and invite the concern of the Association of South East Asian Nations (ASEAN) states because it is a threat to all of us," del Rosario told reporters.

Beijing dismissed Manila's concerns Thursday, saying that "small countries" should not play up disputes.

China's retort came after US assistant secretary of state Daniel Russel commented on the dispute that "bigger nations can't bully the small".

Asked about the remarks, Chinese foreign ministry spokeswoman Hua Chunying said at a regular briefing: "China always maintains that countries, big or small, are equal in international relations.

"We are opposed to big countries bullying small ones, and meanwhile, we believe that small countries cannot make trouble out of nothing," she added.

Manila accused Beijing last year of reclamation work in the Cuarteron, Johnson, Johnson South and Gaven reefs in the Spratly group, which the Chinese call Nansha.

China claims almost all of the South China Sea, a claim which conflicts with those of ASEAN members Brunei, Malaysia, the Philippines and Vietnam as well as non-member Taiwan.

Beijing has previously rejected Philippine protests, saying that the land reclamation was being conducted in Chinese sovereign territory.

A People's Liberation Army Major General Luo Yuan defended China's actions as "justifiable" in state media.

While the Philippines and Vietnam have been vocal in accusing China of aggressive actions, other ASEAN members have been reluctant to criticise the regional giant.

Del Rosario said he would raise the issue at an upcoming meeting of ASEAN foreign ministers, pushing for countries involved in the dispute to adhere to a code of conduct to not increase tensions in the maritime region.

He said the Philippines hoped to receive a positive decision by early next year to the formal plea it filed to the United Nations last March challenging China's claims.