MANILA - The Philippines claimed that the continued presence of Chinese vessels in Manila's maritime territory in the South China Sea revealed that Beijing plans to occupy more features in the disputed waterway.

Philippine Defense Secretary Delfin Lorenzana's latest statement came after the Chinese Embassy in Manila a day earlier defended the presence of Chinese boats at the Whitsun Reef saying it was part of "China's Nansha Islands" – Beijing's name for the Spratly Islands.

"China should respect Philippine sovereignty over the Kalayaan Islands, and its sovereign rights over its Exclusive Economic Zone as defined by UNCLOS and affirmed by the arbitral award," Lorenzana said in a statement, referring to the Spratly Islands by its Philippine name, and the United Nations Convention on the Law of the Sea.

The Whitsun Reef is about 175 nautical miles off the Philippine island province of Palawan and within the country's 200-nautical mile exclusive economic zone (EEZ).

"The continued presence of Chinese maritime militias in the area reveals their intent to further occupy features in the West Philippine Sea," Lorenzana said, referring to the South China Sea by its Philippine name.

The Philippine defense secretary was citing a July 2016 U.N.-backed tribunal's ruling that affirmed the Philippines' sovereign rights in the waterway.

China claims the Spratly Islands in addition to almost all of the South China Sea and rejects the tribunal's ruling.

The Philippines had said last month that 220 Chinese ships were seen moored at Whitsun Reef on March 7, and "showed no actual fishing activities." Manila on March 22 lodged a diplomatic protest with Beijing over the presence of the vessels.

Lorenzana said that as of Saturday, 44 of those Chinese vessels were still near the reef and ought to leave. Beijing's earlier explanation that the vessels were fishing boats sheltering in bad weather was not true, he claimed.

"I am no fool. The weather has been good so far, so they have no other reason to stay there. These vessels should be on their way out," Lorenzana said.

"The Chinese Ambassador has a lot of explaining to do."

'Niu'e Jiao part of China's Nansha Islands'

The Philippine defense secretary's statement was part of an escalating war of words between him and the Chinese Embassy in Manila over the weekend.

The Chinese Embassy in Manila on Saturday denounced Lorenzana's demand from earlier in the day that the Chinese vessels must leave "our sovereign territories." It also called Lorenzana's Saturday statement "perplexing."

"The Niu'e Jiao is part of China's Nansha Islands. The waters around Niu'e Jiao have been a traditional fishing ground for Chinese fishermen for many years," the Chinese Embassy's statement on Saturday said. Niu'e Jiao is the Chinese name for the Whitsun Reef.

"The Chinese fishermen have been fishing in the waters for their livelihood every year. It is completely normal for Chinese fishing vessels to fish in the waters and take shelter near the reef during rough sea conditions. Nobody has the right to make wanton remarks on such activities."

But Lorenzana said on Sunday that he didn't buy that explanation and that China had used similar tactics to occupy Scarborough Shoal and Mischief Reef, which the Philippine calls Panatag Shoal and Panganiban Reef, respectively.

"They have done this before at Panatag Shoal or Bajo de Masinloc and at Panganiban Reef brazenly violating Philippine sovereignty and sovereign rights under international law," Lorenzana said.

In 2012, the Chinese seized Scarborough Shoal, a traditional fishing ground within the 200-nautical-mile Exclusive Economic Zone of the Philippines in the South China Sea, after a two-month standoff with the Philippine Navy

Mischief Reef is one of several submerged natural features in the disputed waterway, which China has reclaimed and transformed into military installations.

'Summon the Chinese ambassador'

Renato Reyes, secretary general of Bayan, or the New Patriotic Alliance, a grouping of left leaning organizations in the Philippines, said Manila needs to get an explanation from the Chinese ambassador.

"Malacanang should summon the Chinese ambassador and ask him to explain his recent statements that insult the Philippines ... and disregards our sovereign rights in our EEZ," Reyes said in a statement, referring to the presidential palace in Manila.

"If he does not change the statements made, he should be expelled from the country. China's overweening arrogance is an affront to our nation. It has illegally annexed Juan Felipe Reef, claiming it as part of China's territory and effectively disregarding our EEZ."

According to Reyes, President Rodrigo Duterte's actions in the past few years and Manila's dependence on COVID-19 vaccines from China had placed Philippines' EEZ "in a precarious position."

Duterte is perceived to have been soft on China's intrusions in Philippine territorial waters in the South China Sea since he assumed office in 2016.

After years of soft-pedaling on the issue, Duterte in September declared that the 2016 international arbitration court's ruling in favor of the Philippines' claims in the South China Sea were "beyond compromise."

A Philippine defense historian and analyst said the economic effects of the COVID-19 pandemic would also hamper Manila's response to the Chinese ships.

"Even though the Philippines is mounting a more aggressive response, complete with protests and sorties and patrols, the dire economic situation of the country may make it difficult for the Manila to sustain such operations," Jose Antonio Custodio, of the Institute of Policy, Strategy and Development Studies, told BenarNews on Saturday.

"Thus, the Chinese expect that once the Philippine activities peter out against them, they will just tighten their hold on the area. Given the pro-Beijing posture of Duterte, he may consider these initial actions as face saving."

Custodio said the Chinese vessels' presence at Whitsun Reef is characteristic of China's "grey zone tactics through its maritime militia to enforce Beijing's outrageous and illegal claims on the South China Sea and West Philippine Sea."

The analyst was referring to China escalating its military build-up in the disputed waterway, by deploying ships and aircraft to the region.

Six other Asian governments – Brunei, Indonesia, Malaysia, the Philippines, Taiwan and Vietnam – have territorial claims or maritime boundaries in the South China Sea. While Indonesia does not regard itself as party to the South China Sea dispute, Beijing claims historic rights to parts of that sea overlapping Indonesia's EEZ.