Manila and Beijing traded accusations about a maritime confrontation Wednesday around the disputed Scarborough Shoal, a day after China submitted a chart of the South China Sea feature’s shore to the U.N. to bolster its claim over it.

China has blocked four Philippine vessels that attempted to “intrude into the territorial waters” of the disputed Scarborough Shoal on Wednesday, the country’s coastguard said.

China claims almost the entire South China Sea, brushing off rival claims from other countries – including the Philippines – and an international ruling that its assertion has no legal basis