A judge has laid out a case for the Philippines' claim over disputed islands, citing his analysis of old maps and calling Beijing's nine-dash line that extends into Southeast Asia a "gigantic historical fraud". Senior Supreme Court Judge Antonio Carpio challenged Beijing's claim to 90 per cent of the 3.5 million sq km resource-rich South China Sea, part of which is also claimed by Manila. The Philippines has filed a case with the United Nations challenging Beijing's claims. Meanwhile, tensions between China and Vietnam have escalated in recent weeks following Beijing's dispatch of an oil rig to waters surrounding another contested island group, the Paracels. Carpio used a recent lecture to present 72 ancient maps - 15 of them of Chinese origin. All supposedly showed China's southern border ending at Hainan. The maps have long been freely available to view through the US Library of Congress, but it is the first time a Philippine official has closely examined the maps. "All these ancient maps show that since the first Chinese maps appeared, the southernmost territory of China has always been Hainan Island, with its ancient names being Zhuya, then Qiongya, and thereafter Qiongzhou," Carpio said. He said it was important to establish that Beijing had no historical claim to the territory, even if "historical facts" can no longer be invoked under the United Nations Convention on the Law of the Sea, because Beijing had warned it was prepared to fight for it. "During his recent visit to the US, General Fang Fenghui , chief of staff of the People's Liberation Army, said that … territory passed down by previous Chinese generations to the present one will not be forgotten or sacrificed," Carpio said. Beijing has always backed its historical claims by saying it has "authoritative maps" but has not made such maps public. Carpio said: "We shall gladly accept China's invitation to look at the historical facts by examining three types of maps" - those made in China, those made by foreigners, and ancient maps of the Philippines showing the disputed Huangyan island as part of the archipelago and not China. Carpio is familiar with the dispute, having signed a Supreme Court decision affirming the constitutionality of the Philippine "archipelagic baseline law" which staked ownership over islands in the South China Sea. During his lecture on the maps last Friday, Carpio said it was important to show that the nine-dash line was a "gigantic historical fraud" because China was using it to court public opinion. The first map Carpio showed was a photo of a rubbing of a map engraved in stone in Fuchang in 1136 AD in the Song dynasty. He said "the stone map shows Hainan island as the southernmost territory of China". Ten years ago, the Chinese embassy in Manila cited an inscription on the tomb of Hainan garrison general Quian Shicai of the Ming dynasty as evidence of China's claim over the Spratly islands. It stated: "Guangdong is adjacent to the grand South China Sea, and the territories beyond the sea all internally belong to the Ming state." But Carpio showed five official maps from the Ming dynasty showing "Hainan as the southernmost territory of China". The Chinese embassy has also said that in the Qing dynasty, China marked the Nansha Islands on authoritative maps and exercised administrative jurisdiction over the islands. But Carpio presented three official maps from the Qing dynasty that he said showed Hainan as China's most southern territory.