MANILA -- While sailing toward the Philippine-occupied Commodore Reef in the South China Sea, a Philippine Navy vessel spotted a gray ship and made radio contact. The response was blunt.

"The Chinese government has immutable sovereignty over the South China Sea, its islands and its adjacent waters."

The gray ship belonging China's People's Liberation Army Navy directed its fire control radar at the Philippine vessel, indicating "hostile intent," according to the Philippine Navy.

The encounter, which ended peacefully and was belatedly disclosed by the Philippine government on Thursday, took place on Feb. 17 while the coronavirus crisis was engulfing China. But as Southeast Asian nations fight widening outbreaks of their own, observers say Beijing has renewed efforts to consolidate its control over disputed parts of the South China Sea, ratcheting up tensions among rival claimants.

U.S. Secretary of State Mike Pompeo on Thursday accused China's Communist Party of "exploiting the world's focus on the COVID-19 crisis by continuing its provocative behavior."

In a video conference with Southeast Asian counterparts, Pompeo attacked China's "new unilateral announcement" of two new administrative districts in the South China Sea, its sinking of a Vietnamese fishing vessel this month, and its "research stations" on Fiery Cross Reef and Subi Reef.

Pompeo also said China continued to deploy maritime militia around the Spratly Islands and recently dispatched "a flotilla that included an energy survey vessel for the sole purpose of intimidating other claimants from engaging in offshore hydrocarbon development," in an apparent reference to a standoff between China and Malaysia.

"The U.S. strongly opposes China's bullying and we hope other nations will hold them to account too," Pompeo said.

China's Foreign Ministry Spokesperson Geng Shuang on Thursday countered Pompeo's remarks, saying "China will always resolutely safeguard its sovereignty, security and development interests, no matter what, no matter when."

"Some people in the US want to replace facts with rumors and lies and sow discords among neighbors," Geng said in a regular press briefing.

Analysts said the actions pointed out by Pompeo have been part of Beijing's standard operating procedures in the South China Sea.

"The only difference is that Beijing is exploiting the very fact that its Southeast Asian rivals in the South China Sea are having their hands full trying to contain the pandemic and its economic consequences, with the hope they would either not respond or do so sub-optimally against China's moves to further consolidate its gains in the South China Sea," said Collin Koh, maritime security expert at the Institute of Defence and Strategic Studies in Singapore.

Gregory Poling, director at the Asia Maritime Transparency Initiative, said some of Beijing's announcements, including the new districts for the islands and a list of 80 newly named features "were probably in the works for months or years but may have been given final approval either to take advantage of what Beijing sees as a window of opportunity or as part of the Ministry of Foreign Affair's more nationalistic tone lately."

China claims most parts of the South China Sea and undertook massive reclamations, including in areas that Southeast Asian nations Brunei, Malaysia, Philippines and Vietnam claim are part of their respective territories.

Taking a cue from Hanoi, Manila on Wednesday filed diplomatic protests against the new Chinese districts as well as the Feb. 17 incident in a move, which Koh said indicates "growing wariness" over Beijing even as it sends aid to Manila to fight the coronavirus. Malaysia, meanwhile, has called for calm, urging all parties to keep communication lines open.

Amid rising tensions, U.S. and Australian warships sailed in the disputed waters, near an area where a Chinese survey vessel Haiyang Dizhi 8 has been operating close to a drillship contracted by Malaysian state oil company Petronas, Reuters reported last week, citing regional sources.

The U.S. Pacific Command confirmed a U.S.-Australian naval exercise, but did not indicate its exact location. It said Australian frigate HMAS Parramatta began sailing with Ticonderoga-class guided missile-cruiser USS Bunker Hill then rendezvoused with amphibious assault ship USS America and Arleigh-Burke class guided missile destroyer USS Barry on April 18.

IDSS's Koh said the U.S. Navy presence signals Washington's commitment at a time when some of its forces are down with the virus. U.S. in March canceled its largest military exercise with Manila that was set for May due to the pandemic.

"I believe we may still see Australian forces remaining active in the South China Sea, conducting its routine naval presence," Koh said.

Even so, Poling does not expect Beijing to slow operations in the South China Sea, saying "the sky's the limit" for its next moves.

"China's coast guard and militia boats will continue to harass fishing and oil and gas operators across the region, so the next crisis is a matter of time," Poling said.

He said Beijing could set up an air defense identification zone or a platform for radar and intelligence gathering at the Scarborough Shoal, which it took over following a stand-off with Manila in 2012.

"I don't necessarily expect any of those tomorrow, but they are all going to happen sooner or later."