China and Vietnam have hurled accusations at each other for weeks over what each sees as intrusions into its territorial waters by the other in a swath of ocean crossed by key shipping lanes and thought to hold large deposits of oil and gas.

Such accusations are not uncommon between China, Vietnam and the Philippines, Malaysia, Brunei and Taiwan, which are also involved in long-standing maritime disputes in the South China Sea, but this bout of tension has run longer than usual.

The senior navy source, who declined to be identified, said the naval drills were "routine", pre-planned and not related to the territorial disputes.

"We shouldn't pay too much attention to them so as to not add to the tension. They're not aimed at confronting any country," said the source, who declined to be identified. He declined to confirm that the drills were under way.

An article in the Vietnamese newspaper People's Army on Sunday blamed China for creating disputes "through provocative actions, hostilities aimed at its neighbours and threats to the interests of maritime navigation of other countries (that) will not bring good results for China".

"Threatening to use force in the Eastern Sea runs counter to the trend of peace and cooperation in the region and the world and makes the environment in the region and the world less stable," it said, using Vietnam's term for the South China Sea.

Two sessions of live-fire naval drills were scheduled for Monday in the sea off the coast near the town of Hoi An, a popular tourist destination south of Danang.

The Vietnamese foreign ministry declined to comment on the drills on Monday, but described them last week as "routine".

China's Global Times, a popular tabloid with a nationalist bent run by Communist Party mouthpiece the People's Daily, said the drills were "a military show of force to defy Beijing".

In Vietnam, the government has actively publicised two incidents in recent weeks in which it says Chinese vessels intentionally damaged gear in use by Vietnamese seismic survey vessels in Vietnamese waters, including within Vietnam's 200 nautical mile (370 km) exclusive economic zone.

China has denied that its ships have done anything wrong.

Computer hackers on both sides of the border have taken matters into their own hands, according to media accounts, posting pro-China or pro-Vietnam messages on scores of the other country's websites, including some belonging to the government.

On Monday, Hanoi publicised a June 10 directive from Prime Minister Nguyen Tan Dung ordering government agencies to enhance their digital security and develop contingency plans in the face of "serious threats".

The Philippines, which has also quarrelled with China recently over maritime territory, said on Monday it would refer to the South China Sea as the West Philippine Sea from now on.

Copyright Reuters, 2011