BEIJING (AP) — Chinese authorities have detained another activist as they try to suppress commemorations of next week’s 25th anniversary of the 1989 crackdown on the Tiananmen Square pro-democracy protests.

Lawyer Zhang Xuezhong said Friday that Wang Aizhong, a founder of the Southern Street Movement, was detained in the southern city of Guangzhou on suspicion of picking quarrels and provoking troubles.

Wang is at least the 20th person detained ahead of the anniversary of the June 4, 1989, military attack on protesters. Others have been put under house arrest.

Communist leaders detain and harass activists every year ahead of June 4 but this year’s efforts to suppress China’s small number of active dissidents are unusually severe.