The Philippines said Wednesday it would push ahead with plans to expand oil and gas exploration in waters also claimed by China, as it brushed off a fresh Chinese warning.

The comments came amid a fresh spike in tensions in the decades-old dispute over the potentially resource-rich South China Sea, where the Philippines and China, as well as Brunei, Malaysia and Taiwan, have overlapping claims.

Philippine Energy Undersecretary James Layug said it was preparing to issue exploration licences for 15 blocs, three of which were in the South China Sea.

However Layug insisted China had no legal claim to the three contentious blocs, as they were well within the Philippines' 200-nautical-mile economic exclusion zone recognised under international law.

"In our view, (these) areas are not disputed areas... that they are our territory has been accepted by all our neighbours, except China," Layug told reporters.

He said the three licences were for areas between 72 and 80 nautical miles from the western Philippine island of Palawan, and 575 nautical miles from the nearest major Chinese landmass.

Layug said 36 companies, including major foreign oil companies such as Total, Esso and Mitra, had submitted applications by Wednesday's deadline to bid for the 15 licenses.

The other 12 licenses on offer are in Philippine territory not claimed by China.

At this stage of the process, companies are only required to submit a general application to explore for any of the 15 blocs. They have to nominate which specific bloc they want to explore by the end of July.

Chinese foreign ministry spokesman Hong Lei hit out on Tuesday in Beijing at the Philippine exploration plans.

"Any country or company that engages in oil and gas activities in waters under Chinese jurisdiction without the Chinese government's approval does so illegally," he said.

Philippine Foreign Secretary Albert del Rosario reacted to Hong's comments on Wednesday by reasserting his country's rights to the areas, as determined by the UN's Convention on the Law of the Sea.

"It is our stated position that our activities are well within our sovereignty under UNCLOS," del Rosario said.

The Philippines has issued only one previous exploration licence for a bloc in waters also claimed by China -- in an area called Reed Bank about 80 nautical miles from Palawan.

Tensions between the two countries spiked last year after the Philippines said Chinese patrol boats harassed a British vessel doing survey work in that area, disrupting its work.

The reported harassment in Reed Bank was one of many increasingly aggressive actions the Philippines accused China of taking last year to assert its claims over the disputed waters.