China on Friday said that Vietnamese ships have rammed its vessels more than 1,500 times since early last month, as the two countries increasingly trade accusations over a South China Sea territorial dispute.

At a special briefing with reporters Friday, Chinese foreign ministry official Yi Xianliang accused Vietnamese vessels of ramming Chinese ships near an oil rig in contested waters a total of 1,547 times since May 2.

Vietnam now has 61 ships in the area while China has 71, including government and auxiliary ships, Yi said.

Relations between Vietnam and China have plummeted over the oil rig's presence, worsening an increasingly heated row over territorial claims in the area.

Anti-Chinese riots sparked by Beijing's dispatch of the rig claimed three Chinese lives in Vietnam last month, according to Hanoi. Beijing says four Chinese citizens died in the unrest.

Friday's briefing appeared to be the latest in a series of efforts by both countries to sway international opinion on the dispute.

Last week, Vietnam released dramatic footage showing a large Chinese ship chasing and ramming one of its fishing boats which then sank near the rig.

Then on Thursday, Hanoi submitted a position paper to the UN General Assembly ordering Beijing to withdraw its oil rig from waters near the Paracel Islands and stop "interfering" with maritime safety.

The document was in response to a similar effort by Beijing this week.

At Friday's briefing, China showed video and photographs of several of the alleged clashes, which Yi said took place on May 2 and 3.

Three videos -- taken by crew members on their cell phones, according to Yi -- appeared to show Vietnamese ships ramming Chinese vessels.

A fourth clip showed a half dozen Chinese crew members salvaging tangled fishing nets and large pieces of wood from the water, which Yi said were deployed "intentionally" by Vietnam to obstruct the Chinese ships.

Yi also cast doubt on the May 26 sinking incident, arguing that the fact that the crew members were quickly able to board other ships "shows that they may not be fishermen at all".

He maintained that "there is no dispute whatsoever over the Xisha Islands," China's name for the contested Paracels.

"The words of Vietnam will not determine whether there is a dispute over the islands or not," Yi said.

"We are living in the 21st century," he added. "If any country can lay its claim over islands simply by saying that there is a dispute over it, the world will fall into chaos."