The defense lawyer for the head of the Bahrain Center for Human Rights says his client was ordered detained for seven days over a tweet in which he said that many Bahraini men who joined terrorist groups like the Islamic State group came from the country's own security institutions.

Nabeel Rajab was detained Wednesday for questioning. Lawyer Jalila al-Sayed says Rajab was referred to the public prosecutor Thursday and ordered to remain in detention another seven days pending investigation.

The Interior Ministry says Rajab was summoned because his tweet "denigrated government institutions."

Rajab wrote that security institutions are "the first ideological incubator" for Bahrainis who joined the Islamic State group fighting in Iraq and Syria.

He previously served two years in prison for leading anti-government Shiite protests.