MANILA (REUTERS) - China's embassy in the Philippines has blamed "some external countries" for stoking tensions in the region, in remarks aimed at Japan after its ambassador stressed the need for peace and stability in the South China Sea.

China was criticised by the Philippines and the United States this week after Manila said there were about 220 vessels likely manned by Chinese maritime militia anchored in disputed waters.

"Within our region, tensions are rising because some external countries are bent on playing fusty geopolitical games," the Chinese embassy said on Twitter.

"It is a pity that some Asian country, which has disputes in the East China Sea and is driven by the selfish aim to check China's revitalisation, willingly stoops as a strategic vassal of the US," it said.

The comment was a direct response to a Twitter remark by Japan's ambassador to the Philippines, Mr Koshikawa Kazuhiko, who on Tuesday said his country "opposes any action that heightens tensions" in the South China Sea and supports international efforts to keep the waters peaceful and open.

China's extensive territorial claims in the East and South China Seas have become a priority issue in an increasingly testy Sino-US relationship and are a security concern for Japan.

The Philippines complained to China at the weekend about what it called the "swarming and threatening presence" of Chinese vessels at the Whitsun Reef.

China's mission in the Philippines said those were fishing vessels sheltering from rough seas. It also criticised the United States for "fanning flames and provoking confrontation in the region".

Philippine military chief Cirilito Sobejana on Wednesday said he had instructed the navy to deploy more boats "to increase our visibility and ensure the security and safety of our fishermen".

Lieutenant-General Sobejana said China's defence attache had met Philippine military representatives on Wednesday after being asked to explain the maritime militia, but he had yet to briefed on the meeting.