A Chinese writer based in Germany says police in his hometown are holding three of his siblings in retaliation for an article he wrote condemning the detention of a fellow writer suspected of involvement in the posting of an anonymous letter online calling for the Chinese president's resignation.

Zhang Ping, better known by his penname Chang Ping, said Monday that his two younger brothers and a younger sister were detained after they returned to the southwestern town of Duofu to celebrate their father's birthday.

Zhang said police were demanding that he give up his column on the website of German international broadcaster Deutsche Welle.

Asked by phone about Zhang's siblings, Duofu police said they are holding several people on suspicion of arson but refused to give details.