WASHINGTON (BLOOMBERG) - The US expressed concern on Tuesday (March 23) over the presence of more than 200 Chinese fishing vessels near a disputed South China Sea reef, saying Beijing uses "maritime militia to intimidate, provoke and threaten other nations".

Chinese boats "have been mooring in this area for many months in ever increasing numbers, regardless of the weather", the US Embassy in the Philippines said in a statement.

China earlier said that its vessels near Whitsun Reef were sheltering from the wind.

"We stand with the Philippines, our oldest treaty ally in Asia," the embassy said.

Manila has filed a diplomatic protest with China and called for the Chinese vessels to immediately leave what it considers part of its exclusive economic zone.

The incident comes amid continued tensions between the US and China, and as the Philippines under President Rodrigo Duterte builds friendly ties with Beijing while maintaining its alliance with Washington.

Mr Duterte will discuss the incident with China's envoy to Manila, presidential spokesman Harry Roque said on Tuesday, while repeating that the two nations can talk things out as friends.

More than 180 vessels were still near the reef, the Philippine military said after patrolling the area on Monday.