China says French ship entered its waters illegally

China on Thursday said it has complained to France after a French warship entered Chinese territorial waters while passing through the Taiwan Strait this month.

In a related development, Chinese Vice Premier Hu Chunhua blamed British activity in the South China Sea for a downturn in relations in comments at the start of a meeting with British treasury chief Philip Hammond.

The complaint and Hu's comments appear to illustrate how China is now willing to permit assertions of its territorial claims to affect ties with nations from outside the region.

The April 7 incident in the Taiwan Strait marks a rare case of military friction between the two countries, which have held joint search and rescue exercises before.

Defence Ministry spokesman Ren Guoqiang said the navy dispatched ships to identify, warn and escort the French ship and would remain "highly alert to firmly safeguard China's sovereignty and security." It was not immediately clear whether France had responded to the Chinese complaint.

The 160-kilometer (100-mile) -wide Taiwan Strait divides mainland China from Taiwan, which Beijing claims as its territory. It is considered an international waterway heavily trafficked by ships from all nations, many of them bound for Chinese ports.

However, China is highly sensitive to operations by foreign warships near areas it claims, such as the South China Sea, where it has built military installations atop seven man-made islands.

American allies such as France, Australia and Britain have been increasing their presence in the region, just as the US Navy is stepping up its "freedom of navigation operation" missions near Chinese island holdings, enraging Beijing.

In his remarks to Hammond, Hu appeared to reference one such mission by a British warship last August.

At the time, China denounced the passage of the British warship HMS Albion close to Chinese-claimed islands in the South China Sea's Paracel group, in a development seen as possibly affecting negotiations on a post-Brexit trade agreement between the sides.

"It is regrettable that since August last year the relations between our two countries witnessed some fluctuations because of the South China Sea issue and a series of institutional dialogues and cooperation projects had to pause," Hu said.

"The South China Sea issue concerns the sovereignty and core interests of China and it is highly important and sensitive in relations between China and Britain," he said.

Hammond responded that he shared Hu's "regret that over the last few months there have been some difficulties in advancing the positive course of the relationship that our leaders have set out."