Lu Gengsong's home is searched, although no reason is given for the charges.
Tibetan blogger Woeser is placed under house arrest after an invitation from the U.S. Embassy.
China's president warns against further confrontation between the two countries.
His family say police detained him first, then sought out evidence to bring against him in trumped-up charges.
The German chancellor had requested to speak with the dissident's relatives.
Journalists and political commentators say freedoms in the city are in a state of emergency.
Seven of the arrests follow a public commemorative event in Henan province on the 25th anniversary of the bloodshed.
The chief executive says Beijing won't agree to the open nomination of election candidates.
The blocks may be linked to massive pro-democracy demonstrations in Hong Kong Tuesday, netizens say.
An international rights group says the right to protest peacefully is enshrined in international law.
At least 2,000 are taken away to a detention center in buses, witnesses say.
Organizers say some half a million people took to the streets in the rain.