MANILA, Philippines -- The United States deployed two warships on Wednesday in a disputed South China Sea shoal, where two Chinese navy and coast guard ships collided two days ago while trying to drive away a smaller Philippine ship in a high-seas accident captured on video, alarming several Western and Asian countries.

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.

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