Chakib Khiyari, the chairman of the Rif Association for Human Rights, was arrested during a police raid in his house in the northern Morocco town of Nador on Wednesday, said the association's deputy head, Mohammed Hamouchi.
About 10 plainclothes officers from the Casablanca-based National Brigade police unit along with police officers searched Khiyari's house and confiscated his computer, Hamouchi said.
Colleagues have had no news from the rights group leader since then, they said.
The association focuses on promoting human rights in the Rif, a remote region of northern Morocco inhabited mostly by the Berber ethnic minority and where most of the country's hashish is grown. Morocco is the world's second-largest hashish producer and has vowed to crack down on drugs.
Officials at Morocco's Interior Ministry could not be reached for comment Thursday.
Hamouchi suggested Khiyari's arrest could be linked to his accusations that several police officers were involved in drug trafficking. The human rights group sent a letter to Morocco's King Mohammed VI naming some security forces members allegedly involved in the illegal trade.
In January, 29 Royal Marines, 17 police and 15 members of auxiliary services were among a group of 81 people arrested in Morocco on charges of involvement in an international drug ring.
The Interior Ministry says it seized 97.5 U.S. tons (88.5 metric tons) of cannabis in a 10-month period in 2008.
From Associated Press.