Vietnam says a Chinese vessel intentionally rammed two of its ships in a part of the disputed South China Sea where Beijing has deployed a giant oil rig, sending tensions spiralling in the region.

The Foreign Ministry in Hanoi said the collisions took place on Sunday and caused considerable damage to the Vietnamese ships. Six people suffered minor injuries, it said.

“On May 4, Chinese ships intentionally rammed two Vietnamese Sea Guard vessels,” said Tran Duy Hai, a Foreign Ministry official and deputy head of Vietnam’s national border committee.