Vietnam has protested to Beijing over its activities in the South China Sea. It's demanding that a Chinese survey vessel and escort ships leave Vietnamese waters.

A spokesperson for the Vietnamese Foreign Ministry released a statement on the presence of Chinese ships in Vietnam's exclusive economic zone.

Pham Thu Hang said her country has contacted China multiple times over the issue and taken other steps in line with domestic and international laws.

Hang pointed out Vietnam's EEZ is set under the UN Convention on the Law of the Sea.

She also criticized China's recent placement of three light buoys near the disputed Spratly Islands. She said the move violates Vietnam sovereignty over the area.

China reacted sharply to Vietnam's claims.

Chinese Foreign Ministry Spokesperson Mao Ning said, "Chinese ships carry out normal activities within China's jurisdiction. It is legitimate and lawful, and there is no issue of entering other countries' exclusive economic zones."

China's claim to nearly all of the South China Sea is rejected by other countries in the region. The feud has sparked violent protests in Vietnam in the past.