China accused Indonesia Sunday of firing on its fishermen and injuring one of them, in the latest flare-up of tensions between the two nations in the South China Sea. The foreign ministry in Beijing launched a strong protest over what it termed the Indonesian navy's harassment of Chinese fishermen. It said several Indonesian naval ships opened fire on the boats in a disputed fishing ground on Friday. One crew member was injured, it said without giving details, while another fishing boat and seven crew were detained. "China strongly protests and condemns such excessive use of force," ministry spokeswoman Hua Chunying was quoted as saying in a statement carried by the official Xinhua news agency. The agency said the incident took place in a "traditional Chinese fishing ground" where the two countries have overlapping maritime claims. Indonesia's actions violated international laws, Hua was quoted as saying. "China urges Indonesia to stop taking action that escalates tension, complicates issues or affects peace and stability," she said. Indonesia's navy confirmed the incident in a statement, saying a Chinese-flagged vessel was detained, but that nobody was harmed. The navy said it intercepted 12 foreign vessels illegally fishing which fled as the warships approached. Navy vessels pursued and fired several warning shots, until eventually a Chinese-flagged ship was stopped and boarded, the statement said. Navy spokesman Edi Sucipto said all seven crew aboard were unharmed. "All the crew are safe. The six men and one woman are now in Ranai," he told AFP, referring to the navy base. "Whatever the flag, when they commit violations inside Indonesia's jurisdiction, we, in this case the navy, will not hesitate to act decisively," he added in a statement. Beijing late last month lodged a strong protest after the Indonesian navy seized a Chinese boat in waters near Indonesia's Natuna Islands for allegedly fishing illegally. The two sides have clashed before over the islands on the southwestern edge of the South China Sea. In March Chinese coastguards rammed a Chinese boat detained near the Natunas and helped it escape as the Indonesians towed the vessel to shore. Jakarta responded furiously, lodging a protest and summoning China's top envoy in the country. China asserts authority over almost all the South China Sea despite partial counter-claims from several Southeast Asian nations. Unlike its neighbours, Indonesia does not dispute ownership of reefs or islets in the sea. But it objects to Beijing's claims because they overlap with its own exclusive economic zone around the Natunas. Indonesia has launched a tough crackdown on illegal fishing in recent months, sinking foreign boats after removing the crews.