Chinese scientists landed on a disputed South China Sea reef over the weekend in the latest assertion of Beijing’s sovereignty claims.

The uninhabited sandbank, Sandy Cay, has become a growing flashpoint following a series of encounters between Chinese and Philippine coastguard, military and fishing vessels.

The Philippines said the Chinese-flagged research vessel Xiang Yang Hong 33 had been spotted near the reef on Saturday, escorted by two coastguard ships.

Jay Tarriela, a spokesman for the Philippine coastguard, said “Chinese personnel were observed landing and conducting illegal activities”.

He added that the coastguards carried out a “maritime domain awareness flight” on Sunday to “address and drive away unauthorised marine scientific research activities”, adding that such actions constituted a violation of Philippine sovereignty and the United Nations Convention on the Law of the Sea.

Tensions between Beijing and Manila have been rising over the past few weeks, with Manila accusing Beijing of deploying maritime militia and coastguard ships in contested areas of the South China Sea.