The Philippines condemned Tuesday the “aggressive” actions of a Chinese security vessel, which is accused of using a military-grade laser light against a Philippine patrol boat in the disputed South China Sea, leaving crew members temporarily blinded.

The incident happened on February 6, nearly 20 kilometers (12 miles) from Second Thomas Shoal in the Spratly Islands, where Philippine marines are stationed in a derelict navy ship grounded to assert Manila’s territorial claim in the waters.

The Department of Foreign Affairs said it had filed a diplomatic protest to the Chinese embassy in Manila over the “latest aggressive activities of the Chinese Coast Guard against Philippine official vessels” near the shoal.

There have been a series of maritime incidents between the Philippines and China, which claims sovereignty over almost the entire South China Sea and has ignored an international court ruling that its claims have no legal basis.

Chinese foreign ministry spokesman Wang Wenbin said Monday the Philippine boat had “intruded” into China’s sovereign waters without permission.

He said the Chinese Coast Guard personnel had acted in a “professional and restrained” manner.

Days before the latest incident, the United States and the Philippines agreed to resume joint patrols in the sea, and struck a deal to give US troops access to another four military bases in the Southeast Asian country.

US State Department spokesman Ned Price on Monday criticized the Chinese Coast Guard’s actions as “provocative and unsafe”.

“The United States stands with our Philippine allies in the face of the People’s Republic of China Coast Guard’s reported use of laser devices against the crew of a Philippine Coast Guard ship,” Price said.

The Philippine patrol boat was supporting a “rotation and resupply mission” for the marines in Second Thomas Shoal when the Chinese vessel pointed the laser light at them twice, the Philippine Coast Guard said Monday.

The Chinese boat also issued illegal radio challenges and undertook dangerous maneuvers, which “constituted a threat to Philippine sovereignty and security as a state”, the foreign ministry said.

“These acts of aggression by China are disturbing and disappointing as it closely follows the state visit to China of President Ferdinand R. Marcos Jr.,” foreign ministry spokeswoman Teresita Daza said.

Marcos and his Chinese counterpart Xi Jinping agreed last month to “manage maritime differences through diplomacy and dialogue, without resorting to force and intimidation,” Daza said.

Price said that China’s “dangerous operational behaviour directly threatens regional peace and stability, infringes upon freedom of navigation in the South China Sea… and undermines the rules-based international order.”

The US-Philippine deal earlier this month brings to nine the total number of Philippine bases accessible to US forces.

It comes as the long-time allies seek to counter China’s military activity in the region.

Vietnam, Malaysia, and Brunei also have overlapping claims to parts of the South China Sea.