A Chinese security vessel is alleged to have fired a military-grade laser light against a Philippine patrol boat in the disputed South China Sea, prompting Philippine President Ferdinand Marcos to call Beijing's ambassador on Tuesday.

The incident signals an intensification of the diplomatic dispute after the Philippine foreign ministry earlier lodged a protest with the Chinese embassy denouncing the "aggressive" conduct of the Chinese coast guard vessel, which it claimed briefly blinded Filipino crew members.

On Feb. 6, a laser incident occurred about 20 kilometers from Second Thomas Shoal in the Spratly Islands, where Philippine marines are stationed in a decommissioned navy ship that is grounded to enforce Manila's maritime claims.

It is the most recent in a string of maritime incidents between China and the Philippines. China has defied a judgment from an international court that says its claims to control nearly the entire South China Sea are unfounded.

Wang Wenbin, a spokeswoman for the Chinese foreign ministry, asserted that the China Coast Guard had "operated with professionalism and restraint." The nations had been in touch via a hotline established between their respective foreign ministries to talk about marine issues, according to Wang.

According to spokeswoman Cheloy Velicaria-Garafil, Marcos confronted Chinese ambassador Huang Xilian "over the increasing frequency and intensity of actions by China" against the Philippine Coast Guard and Filipino fishermen. The Chinese embassy claimed that the men had spoken about how to "properly manage maritime differences between China and the Philippines".

Days before the most recent incident, the U.S. and the Philippines reached an agreement to restart combined maritime patrols and to grant US.. forces access to four more military bases in the Southeast Asian nation.

Ned Price, a spokesperson for the U.S. State Department, criticized the China Coast Guard's conduct as "provocative and unsafe" on Monday."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.

Commodore Jay Tarriela, a maritime security consultant for the Philippine Coast Guard said it wasn't the first time a Chinese coast guard boat has pointed a laser light at a Philippine vessel. The crew of a Philippine Coast Guard boat experienced temporary blindness and skin irritation after being exposed to blue light for over 20 minutes which happened in June last year.

The number of Philippine sites available to the U.S. military has increased to nine as a result of the U.S.-Philippine agreement earlier this month. The long-time partners are trying to counteract Chinese military activity in the area at the time. In the South China Sea, there are also conflicting claims from Vietnam, Malaysia, and Brunei.