A Chinese former navy captain who many claim is a defector stunned Taiwan’s navy on Sunday when he drove his speedboat to a pier directly outside the capital, Taipei.

The intrusion by a mainland Chinese man despite high security measures amid repeatedly escalating tensions with China has been strongly criticised by Taiwan’s top politicians.

China regards Taiwan as a rebel province that must be reunified with the mainland, even if done by force.

The 60-year-old man named Ruan was spotted 11 km off the Tamsui coast of New Taipei.

According to the coast guard, the boat collided with a ferry at the pier after entering the Tamsui River heading towards Taipei city, the Hong Kong-based South China Morning Post reported on Tuesday.

Ruan, who described himself as a former Chinese navy captain, said he had left Ningde Port in the Chinese coastal city of Fuzhou a day earlier. However, Taiwan’s coast guard said no food or drink was found on the boat and that the man was not dark skinned.

According to the coast guard, the man said he was persecuted by mainland authorities for “making inappropriate statements” and wanted to flee to Taiwan.

He was accused of violating various Taiwanese laws, including the Immigration Act.

Taiwan’s Defense Minister Wellington Koo said on Tuesday that the possibility that the Chinese speedboat invasion was a grey zone tactic by Beijing could not be ruled out.

Following this, the Defense Ministry will strengthen measures to prevent sudden incursions by ships from China, Taiwan News reported.

Taipei Mayor Hou You-yee called it a serious security lapse, especially considering that the pier is less than a 10-minute boat ride from Taipei.

“No lapse in national border security can be tolerated. This incident shows that the Coast Guard and first-line security reporting mechanisms were not managed effectively,” he said.

China has stepped up military drills with its army, navy, air force and rocket force around Taiwan after pro-independence leader Lai Ching-te of the Democratic Progressive Party (DPP) won presidential elections last month.