According to the board, swimming and diving activities will be banned in Con Son Bay, and many islets and beaches on the island from July 1 until the end of September.

The service will continue in some other areas including Bai Giong-Hon Bay Canh, Bai Cat Lon-Hon Cau, and Hon Tre Lon.

However, tourist boats won't be allowed to anchor in the areas of coral reefs. The board will conduct frequent patrols to deal with violations and ensure the coral is protected.

Con Dao National Park announced on May 30 that coral had been bleached and died after a check conducted in some areas starting on May 28.

"The coral bleaching has happened in waters off the Con Dao Islands since April due to hot weather," the park said, adding that coral grows well in temperatures of between 24-30 degrees Celsius. However, the local seawater has temperatures of over 32 degrees Celsius due to the El Nino phenomenon, resulting in coral bleaching.

"It will be very difficult for the coral to recover and develop if the high temperatures continue," the park noted.

The centre also warned that the El Nino phenomenon would continue with prolonged hot weather, worsening the situation and killing the bleached coral reefs.

In 1998, 2010, and 2016, the sea off the Con Dao Islands also saw coral bleaching due to the El Nino phenomenon, which caused coral deaths in some areas. Con Dao National Park managed to revive the coral later.