Malacanang said on Thursday the Chinese warships' recent incursion in the Philippine waters, particularly in southern Sibutu Strait, was not an act of friendship.

In a press briefing, Presidential Spokesperson Salvador Panelo said the latest Chinese act could be another subject of a diplomatic protest.

"We express concern with that kind of incident. Because if they (China) keep on saying that we’re friends, I don’t think this is an act of friendship," he said.

The Armed Forces of the Philippines Western Mindanao Command has said that they monitored the presence of two Chinese warships and three other vessels last July and this month of August, respectively, in Sibutu Strait off Tawi-Tawi province.

Early this year and until July, four Chinese warships also entered the Philippine exclusive economic zone.

In all those instances, the defense department and the military have said there were no coordination with the Philippine government.

The ships even reportedly turned off their automatic identification systems whenever inside the Philippine territory.

Panelo said Chinese warships could have violated the United Nations Convention on the Law of the Sea.

"If there's a violation of the UNCLOS, we will file a diplomatic protest," he said.

Both the Philippines and China are signatories to the UNCLOS.

Beijing continues to refuse the United Nations arbitral ruling favoring the Philippines while invalidating China's historic and sovereign claim in almost the entire South China Sea using its nine-dash line.

When President Rodrigo Duterte goes to China later this month, Panelo said it would be up to him if he would include the latest incident on the issues that he would bring up with Chinese President Xi Jinping.

"Well, that’s the call of the President. But any issue will always be open between the two heads of state. It's up to the two what they are going to discuss," he said.

Duterte earlier said he would also ask Xi to fast-track completion of the code of conduct in the South China Sea to prevent further problems and the arbitral ruling.

Chinese Ambassador Zhao Jianhua has said China would not change its position with regard to the ruling of the Hague-based Permanent Court of Arbitration.

But Panelo, also chief presisdential legal counsel, said, "And neither are we changing our position too. But it doesn’t mean that as friends, we cannot discuss that issue. It has to be discussed, that is precisely why there is a mechanism for negotiation."

"There are things we can agree upon. There are differences that we may not. But that does not preclude both countries to raise that issue and discuss amicably," he added. Celerina Monte/DMS