BEIJING — Tensions in the South China Sea escalated sharply on Tuesday as China and Vietnam traded accusations over the sinking of a Vietnamese fishing vessel in the vicinity of a Chinese oil rig parked in disputed waters off Vietnam’s coast.

The sinking further aggravated the worsening diplomatic and economic frictions between China and Vietnam, whose relations have plummeted to the worst point in decades after anti-Chinese riots two weeks ago that killed at least four people and injured more than 100 in Vietnam. China evacuated several thousand workers from Vietnam last week.

In the latest incident, a Chinese vessel rammed and sank a Vietnamese fishing boat about 17 nautical miles southwest of the oil rig on Monday afternoon, the state-run Vietnamese television network, VTV1, reported. All 10 crew members were rescued, the network said.