MANILA, Philippines — The U.S. deployed two warships Wednesday in a disputed South China Sea shoal where two Chinese ships collided earlier in the week while trying to drive away a smaller Philippine ship in a high-seas accident that raised alarms about maritime safety.

The Philippines coastguard claims that a fighter tailed one of its aircraft and performed manoeuvres at close proximity.

The Philippines expressed serious concern on Tuesday over what it called "dangerous manoeuvres and unlawful interference" by Chinese vessels during a coast guard supply mission for Filipino fishermen in the Scarborough Shoal in the South China Sea.