BEIJING — A Chinese journalist who had pressed for the release of a prominent human rights activist was detained Friday, one day after the United States completed annual discussions with China on human rights.

The journalist, Chen Min, 51, widely known by his pen name, Xiao Shu, was called to a meeting with security officials in Beijing at around noon Friday. As he was questioned, he kept a friend informed by text message.

In his last message at 1:50 p.m., Mr. Chen said the officers wanted him to leave Beijing and were threatening him, the friend, Wang Gongquan, said. After that, frantic calls and messages to Mr. Chen went unanswered, Mr. Wang said.

Mr. Chen had helped organize a petition calling for the release of Xu Zhiyong, a legal scholar who inspired a grass-roots anticorruption campaign calling for public officials to declare their assets. Mr. Xu, already under house arrest for more than three months, was detained on July 16 for seeking to “gather people and disrupt social order in a public space.”