China is asking Vietnam to investigate reports that a border agent at the Ho Chi Minh City airport defaced a Chinese passport. Images in state media reports show the words “f--- you” scribbled twice over maps of the contested South China Sea. The Chinese consulate in Ho Chi Minh City said in a statement on Wednesday that it strongly condemned the “shameless and cowardly” act and asked Vietnamese officials to investigate and punish the agent. Vietnam president: We oppose China's nine-dash line claim The incident comes at a time of high tensions in the region and weeks after the Hague-based Permanent Court of Arbitration’s ruled this month against China’s claims to the South China Sea. Hanoi has welcomed the verdict, although it has been reluctant to rebuke China. China and Vietnam have had long-running territorial disputes in the South China Sea. Tensions spiked in 2014 after China parked an oil rig near Vietnam’s central coast. China issued new passports starting 2012 with revised maps to include the “nine-dash line,” demarcating Beijing’s claim to nearly the entire South China Sea. Some Vietnamese border agents have begun to issue separate visas rather than stamp Chinese passports to demonstrate that they do not recognize the new map, according to recent media reports in Vietnam.