China denied such allegations, claiming that the ships were seeking shelter at the reef due to rough weather conditions.

The Spratlys are subject to territorial dispute and are in whole or partly claimed by numerous countries, namely Brunei, China, Malaysia, Philippines, Taiwan, and Vietnam.

[7] Up to 220 marine vessels were monitored to have moored in the Whitsun Reef on March 7, 2021, causing concern that the ships are part of prelude to the Chinese government taking control over the maritime feature.

The NTF-WPS reported that the Chinese marine vessels were not engaging in fishing activities and noted the clear weather in the vicinity at around that time.

The NTF-WPS also took note of the incident due to "possible overfishing and destruction of the marine environment, as well as risks to the safety of navigation".

[14] On March 21, Philippine Department of National Defense (DFA) Secretary Delfin Lorenzana issued a demand to China to have the marine vessels, which he alleged were part of a maritime militia, withdraw from Whitsun Reef; calling the mooring as an act of incursion.

[11] The country's Department of Foreign Affairs also filed its first diplomatic protest against Chinese maritime presence in the reef following recommendation from the Philippine military.

[15] The following day, China's Ministry of Foreign Affairs (MFA) disputed the Philippine claim regarding the situation, saying that the fishing boats took shelter at the Whitsun Reef due to rough sea and wind conditions and insisted that their mooring was normal,[16] also saying, "there is no Chinese Maritime Militia as alleged".

[22] The continued tensions over the Whitsun Reef also elicited remarks from direct aides of President Rodrigo Duterte; his lawyer and former spokesperson Salvador Panelo saying the prolonged Chinese presence in the reef risk "unwanted hostilities that both countries would rather not pursue" and that the Philippines would not be blinded by China's humanitarian aid in reference to China's vaccine donations in response to the COVID-19 pandemic, and spokesperson Harry Roque remarking that the Philippine government won't give up a "single inch" of its territory or EEZ.

[26] The Philippine side maintains it is weighing numerous options to resolve the crisis, including leveraging its partnerships with other countries such as the United States,[28] and expelling a Chinese diplomat.

[38] By May 28, 2021, the Philippines' foreign department has filed its 100th diplomatic protest over Chinese presence within the country's claim exclusive economic zone in the South China Sea.

[40] The Philippine Chamber of Commerce and Industry, Management Association of the Philippines, Makati Business Club, Filipina CEO Circle, Bishops-Businessmen's Conference for Human Development, Judicial Reform Initiative, Cebu Business Club, and Iloilo Business Club issued a joint statement of support calling for China to withdraw the presence of its ships from Whitsun Reef and supporting the Philippine sovereignty claims over the maritime feature.

[41] Australia, Japan, and the United States expressed concerns over the development in the South China Sea in response to the standoff in Whitsun Reef.