TAIPEI (Reuters) - Taiwan said on Tuesday it had apprehended a Chinese activist who had slipped away from his tour group last week, and authorities were deciding whether to deport him or risk fraying relations with Beijing by granting him sanctuary as a political refugee.

Officials declined to say whether 48-year-old Zhang Xiangzhong had formally requested asylum, but his case comes at an awkward time as ties with China have been strained since President Tsai Ing-wen took office in Taiwan last year.

According to media reports Zhang was released in 2016 after spending three years in jail for his involvement in the New Citizens’ Movement in China, a group that advocates working within the system to press for change and clean up corruption.

Taiwan’s immigration authorities said Zhang was picked up on the street on Monday evening. His whereabouts had been unknown since he had left his tour group last week, according to an official of the National Immigration Agency.

Taiwan’s Mainland Affairs Council, the island’s China policy-making body, has said they are ready to review any request from him for asylum, but his case will be vetted first by immigration officers.

“He left his group without notice. From the perspective of our tourism regulation, the immigration authorities absolutely have the authority to apprehend him,” MAC vice chairman Chiu Chui-cheng told Reuters.

“If he intentionally overstays in Taiwan, the immigration authorities can deport him after an investigation,” Chiu said, adding that the government must consider agreements between Taiwan and China regarding cross-strait tourism.

“We can send him back, according to the tourism agreement between both sides.”

Defections from China to Taiwan are fairly infrequent as Beijing keeps a tight control on dissidents leaving the country and few would risk sea-crossing over the heavily patrolled strait dividing the mainland from the island.

Wary of provoking Beijing’s ire, Taiwan does not officially offer asylum to Chinese, but it occasionally allows “long term” stays for political refugees. There are currently about 10 such cases in Taiwan.

Zhang, from Shandong province, has said that a source of inspiration for his asylum request was the wife of Taiwanese activist Li Ming-che, Taiwan’s media reported. She has been attempting to free her husband, currently held by China on suspicion of activities harmful to national security.

China regards Taiwan as a wayward province and it has never renounced the use of force to bring the island back under its control, while proudly democratic Taiwan has shown no interest in being run by Communist Party rulers in Beijing.

Defeated Nationalist forces fled to Taiwan in 1949 after losing a civil war with the Communists, but since a thaw began in the 1980s cross-straits investment has flourished. Relations ran into problems last year following the election of Tsai, whose Democratic Progressive Party espouses formal independence from China.