The United States has reaffirmed its commitment to the defense of the Philippines, following a flare-up of tensions in the South China Sea. Manila has accused a Chinese ship of pointing a laser at one of its patrol ships.

US Defense Secretary Lloyd Austin spoke with his Philippine counterpart Carlito Galvez by phone.

Austin said an attack on a Philippine vessel anywhere in the South China Sea would invoke the US mutual defense commitment under a treaty between the two countries.

The Philippine Coast Guard says a Chinese government ship directed a military-grade laser at its patrol vessel earlier this month near the Spratly Islands.

Beijing claims the ship did not direct lasers at the crew, or cause any damage. It says the Chinese ship was compelled to respond, since the Philippine vessel entered Chinese waters without permission.

But Austin agreed with Galvez that the incident took place inside the Philippines' exclusive economic zone.

They discussed joint patrols in the South China Sea and further cooperation with like-minded countries like Japan, that want a free and open Indo-Pacific.

Manila aims to expand its security cooperation with other countries as well. It's mulling joint patrols with Australia in the South China Sea.