Metro Manila (CNN Philippines, April 1) — The military on Monday confirmed reports that several Chinese vessels have been spotted around Philippine-occupied Pag-asa island, one of the biggest islands in the disputed Spratlys in the South China Sea.

"Indeed there (is) presence of Chinese vessels in the area," Armed Forces of the Philippines (AFP) Spokesperson Edgard Arevalo said in an interview with CNN Philippines' New Day. "The information that we got is the more likely intention is to establish their presence in the area."

Reports circulated over the weekend that hundreds of Chinese ships have been circling the island since the start of the year.

Speaking to CNN Philippines' The Source, AFP Western Command Chief of Public Affairs Captain Jason Ramon said over six hundred ships were reported to have swarmed the vicinity of Pag-asa in the first quarter of 2019. However, Ramon later on clarified that the number only amounted to 275.

Arevalo, for his part, said the exact figure may differ day-by-day as ships in the area "come and go."

"What's happening is they remain stationary in the area. Some come and go, that's why it's quite inaccurate to report the number because some of them come and go. Although some of them stay for a few days or weeks," the spokesperson said.

Professor Jay Batongbacal, director of the Institute for Maritime Affairs and Law of the Sea, told CNN Philippines' Balitaan that the disparity may have been due to repeated sightings of some vessels entering the vicinity.

Chinese ambassador Zhao Jianhua said they are also verifying reports of the number of vessels, and if they have been really surrounding the island.

"We have to verify, that's the first step. I'm sure both sides can handle this issue through diplomatic channels in a friendly manner," Jianhua told reporters following his courtesy call in Malacañang.

Jianhua added the groups near Pag-asa may have only been Chinese fishermen-- and that vessels there were "unarmed."

'Common fishing ground'

The military added they have not received any complaints of harassment from fishermen as of the moment. Ramon said military officials had previously monitored vessels from other countries as the area is a "common fishing ground."

"The vicinity's a common fishing ground for all. So for the past, based on the reports, we have monitored fishing vessels from various countries, including Philippines fishing on the sandbars in Pag-asa Island."

Ramon added the presence of the said vessels should not be a cause for concern.

Opposition Senatorial bet and Magdalo Rep. Gary Alejano on Saturday issued a statement slamming the government for not taking immediate action on the matter.

"The government has been warned two years ago, but President Duterte and his cohorts only downplayed the incidents," Alejano said. "While it is a positive development that the AFP is starting to be transparent on the real situation in the West Philippine Sea, I urge the Duterte administration to act on the rising number of Chinese vessels around Pag-asa Island and protest China's illegal actions. China is establishing a norm there which we cannot alter later on. Every day is a wasted opportunity to assert our sovereignty if we do not act now," he added.

Professor Batongbacal meanwhile addressed the issue of the China's supposed "cabbage strategy" in the territory.

"It's very difficult for us to access and maintain our position because of so many layers of these Chinese control and assets," he said.

Gov't files protest

Malacañang on Monday said the Foreign Affairs Department has already filed a diplomatic protest over the presence of Chinese vessels in the area.

Presidential Spokesperson Salvador Panelo, however, could not provide further details as of writing.

"We will ask them first why. First, if they acknowledge such fact as determined by us. Number 2, ask them why they are doing it. Number 3, we will politely ask them not to… not to do what they are doing," Panelo told reporters.

Contrary to earlier reports, the spokesman also claimed the ships were only "stationary" and "on standby"-- not "circling" the island.

The Defense Department, in a statement, meanwhile said it expects other countries to honor international obligations and protocols.

The department likewise urged Filipino fishermen to continue on with their activities "in our waters and Exclusive Economic Zone."

Troops and a civilian community live on Pag-asa island, a barangay or village within the municipality of Kalayaan in Palawan province.

READ: Palace to file protest if proven that Filipino fishermen are shooed away from Scarborough Shoal

CNN Philippines' Alyssa Rola and Xave Gregorio contributed to this report.