A Vietnamese seismic survey put itself to sea Sunday evening, ten days after it was challenged by Chinese boats while operating in Vietnam's territorial waters.
The Binh Minh 02 of PetroVietnam Technical Services Corporation (PTSC) is accompanied by eight guardian ships, instead of three as before.
The oil exploration trip of the Binh Minh 2 will last in 42 days on the Truong Sa (Spratly) islands.
On May 26, a trio of Chinese boats entered Vietnam's Exclusive Economic Zone and severed cables linking the Binh Minh 02 to sensitive exploratory equipment.
The incident took place in an area called Block 148 about 120 km (80 miles) off the south-central coast of Vietnam from the beach town of Nha Trang, and some 600 km (370 miles) south of China's Hainan island.
Nguyen Hong Quan, the captain of a guardian ship for the Binh Minh 02, said two days after the incident, five Chinese fishing boats and a spy plane were spotted near the waters where the Binh Minh 02 was conducting oil exploration work.
On May 31, the vessel came to Nha Trang Port in Khanh Hoa Province for repair.