Panelo said Duterte was “outraged” over the incident, adding that if the collision was found to be intentional, the Philippines would consider it an “act of aggression”.

“We will cut diplomatic relations, that’s what you do whenever there are aggressive acts,” he said during a press briefing.

However, Chinese foreign ministry spokesman Geng Shuang called the incident “an ordinary maritime traffic accident” and said China was still investigating.

“If the relevant reports are true, regardless of the country from which the perpetrator came from, their behaviour should be condemned,” he added.

Geng said that it was irresponsible for the Philippines to “politicise the incident without verification”.

On Wednesday, Defence Secretary Delfin Lorenzana had criticised the “cowardly action of the suspected Chinese fishing vessel and its crew” for abandoning the Philippine fishermen after their collision with the F/B Gimver 1 and thanking the Vietnamese fishing vessel that rescued the fishermen.

Lorenzana said the rescued Philippine crewmen identified the vessel that hit them as Chinese but added on Thursday the government would investigate this further. There was no immediate comment from Chinese officials.

Lorenzana said the F/B Gimver 1 had been anchored “when it was hit by the Chinese fishing vessel”.

A regional military spokesman, Lieutenant Colonel Stephen Penetrante, said the incident appeared “like a hit and run” with the Chinese vessel immediately moving away after hitting the Philippine boat, in violation of international regulations that require ships to rescue people facing danger at sea.

Ramon Beleno, a political scientist at Ateneo De Dqavoau University, said the decision to leave the Philippine fishermen stranded was “inappropriate”.

“China is our friend,” he said. “The Chinese are allowing us to fish in disputed waters but this [incident] happened. It’s unethical. If an accident happens, whether it’s our friend or not, even if unintentional, the right thing to do is to help those victims.

“The right thing for Beijing to do is to help in the probe and surrender those involved. That’s what we expect from them.”

Ramon Casiple, the executive director of Institute for Political and Economic Reform, echoed those concerns.

“They should not have abandoned the Filipino crew,” he said. “It’s a universal part of behaviour … to save those in need of help. They rammed [the boat] and then left … If that’s true then it’s intentional.”

Jay Batongbacal, a maritime expert from the University of the Philippines College of Law, wrote on Facebook there was “no doubt this was deliberate and intentional”.

“There is no ‘maybe’ here,” he wrote. “The Filipino vessel was anchored in the area of Reed Bank, which is a completely submerged feature. This means the fishing vessel was stationary in open water, with unobstructed sea around it that could have been used easily by the other vessel to avoid hitting the former.

“A running person does not accidentally hit another person standing in the middle of an empty football field. Similarly, one moving vessel does not accidentally collide with an anchored vessel in an empty ocean. It can only be deliberate.

“Departing after the collision without rendering assistance to the vessel and crew in distress further proves the deliberate intention to cause harm.”

In recent years, Chinese ships have blocked or intimidated Philippine military and civilian vessels at Reed Bank and nearby Second Thomas Shoal, where Philippine marines keep watch on board a long-marooned Philippine navy ship while being constantly watched by Chinese coastguard ships in a years-long stand-off.

Presidential spokesman Salvador Panelo said Duterte backs Lorenzana’s actions on the boat sinking and added the abandonment of the Philippine fishermen was “uncivilised as it is outrageous.”

Panelo called on Chinese authorities to investigate the collision and impose sanctions on the Chinese crew.