China plans to deploy three more oil rigs in the South China Sea, a move analysts say demonstrates its determination to explore energy resources "despite maritime tension and harassment" from Vietnam and the Philippines.

Two rigs, Nanhai 2 and Nanhai 5, will be deployed in waters east of Guangdong province by Aug 12, while Nanhai 4 will be towed to the Beibu Gulf close to the west coast of the Leizhou Peninsula in the southernmost part of Guangdong by July 15.

The rig coordinates have been posted on the Maritime Safety Administration's website.

Thursday's announcement came a day after talks between State Councilor Yang Jiechi and Vietnamese Foreign Minister Pham Binh Minh and Prime Minister Nguyen Tan Dung over escalating tensions in the South China Sea ended in deadlock.

Foreign Ministry spokeswoman Hua Chunying said on Friday that the rigs will all be within the recognized coastal waters of Guangdong and Hainan provinces.

"There is no need to read too much into these normal activities," Hua said.

Earlier, the maritime agency also gave coordinates for another rig, the Nanhai 9, to be positioned "within the coastal waters off China's Hainan Island" by Friday this week.

Lu Jianren, lead researcher of the China-ASEAN Research Institute at Guangxi University in Nanning, said China has been working in waters off its coast and near the Xisha Islands for years without controversy.

"However, Chinese companies should take precautions to deal with possible disruptive activities from Hanoi, such as (boat) ramming, which may continue," Lu said.

Ties between Beijing and Hanoi plunged in May when China's CNOOC Group sent a deep-sea oil rig to waters near Zhongjian Island. The island, within Chinese territorial waters, is claimed by Vietnam.

Hanoi sent vessels to ram Chinese ships operating in the waters more than 1,500 times, according to the Chinese Foreign Ministry.

The Philippines asked a UN tribunal on Thursday to speed up its ruling on whether China's claims in the region are in violation of international maritime law. Beijing has refused to take part in the proceedings.

Reuters and AFP contributed to this story.