The sinking of a Philippine fishing boat by a Chinese trawler early this month is splitting public opinion, as President Rodrigo Duterte plays it down as a "little maritime incident", and nationalists accusing him of toeing China's line.

His top Cabinet secretaries fanned out yesterday to news forums and press conferences, and went online to echo his opinion that the Yuemaobinyu 42212, a steel-hulled trawler from Guangdong province, did not ram the wooden outrigger boat Gem-Vir on June 9, describing it as an accident at sea.

The description was similar to how Chinese Foreign Ministry spokesman Geng Shuang had characterised it last week - as "an ordinary maritime traffic accident".

Mr Duterte did not comment on testimonies by the Gem-Vir's crew that the Yuemaobinyu fled after sinking their boat. Instead, he said he would want to hear out what China's investigators had to say first.

Mr Junel Isnigne, 43, the Gem-Vir's captain, said he had dropped anchor at midnight on June 9 on a shallow part of Reed Bank, a seamount in the South China Sea, when the Yuemaobinyu suddenly appeared and rammed his boat.

The Gem-Vir sank. But the Yuemaobinyu, instead of rescuing the boat's crew of 22 men, sailed on.

A Vietnamese fishing boat would later pluck them out of the water and hand them over to a Philippine navy ship. The Philippines has since fallen in with Beijing's explanation.

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Mr Duterte' spokesman Salvador Panelo, who earlier condemned the Yuemaobinyu's "barbaric" action, told reporters on Tuesday that there were "circumstances that give doubt to the version" of the Filipino fishermen.

Yesterday, he shot down calls by a senator to invoke the Philippines' defence treaty with the United States and seek intervention.

"That is reckless and premature… The President doesn't want this to be blown into an international crisis," he said.

Defence Secretary Delfin Lorenzana walked back statements issued by the military's top brass, including the navy chief, that the Yuemaobinyu deliberately sank the Gem-Vir, agreeing with Mr Duterte instead that it was just an "accident".

"Maybe the other side didn't mean to brush against our boat," he said at a news forum yesterday.

But he stuck to his opinion that the Chinese, in fleeing instead of rescuing the Gem-Vir's crew, were "cowardly", and should apologise and offer compensation.

"That statement stands," he said.

Agriculture Secretary Emmanuel Pinol, dispatched by Mr Duterte to liaise with the Gem-Vir's men and their families, said at a separate briefing that the incident should be looked at with "a level-headed perspective". But he did back calls to hold the Chinese trawler's captain criminally liable.

Foreign Affairs Secretary Teodoro Locsin said the government was not "trivialising" the case. "That's just stating the scale of the thing and it's improbable nature which… did not end in the deaths of 22 Filipino fishermen," he said in a tweet.

Mr Duterte's critics in the Senate, meanwhile, continued to hammer at Mr Duterte's tepid response.

Senator Leila de Lima called the government's line a "treasonous defence". Senator Panfilo Lacson called out Mr Duterte's "very self-limiting" stance and "insulting remarks" that left the people "heartbroken".

Online though, Mr Duterte's supporters have been spreading his message and assailing opposition lawmakers for trying to capitalise on the incident to stoke unrest.