Islamabad, Pakistan (CNN) -- An anti-drone activist and journalist from Pakistan is missing after being abducted from his home, his lawyer said Monday.
Kareem Khan was seized from his home in Rawalpindi on the night of February 5th, according to attorney Shazad Akbar.
He was picked up by 20 men, some of them dressed in police uniforms, Akbar said.
"Kareem Khan was my first client in 2010 against U.S. drone strikes in the tribal areas of Pakistan," Shahzad told CNN Monday.
Shahzad said he lodged a complaint with local police but they denied having picked him up.
Khan hails from the tribal area of North Waziristan.
He was due to travel to Europe this week to speak to German, Dutch and British parliamentarians about his personal experience with drone strikes, according to Reprieve, a UK-based charity that provides legal support to prisoners unable to pay for it themselves.
Khan was also involved in legal proceedings against the Pakistani government concerning its failure to investigate the deaths of his son and brother in a drone strike, the charity said on its website.
"We are very worried about Mr Khan's safety," writes Clare Algar, executive director of Reprieve. "He is a crucial witness to the dangers of the CIA's covert drone programme, and has simply sought justice for the death of his son and brother through peaceful, legal routes."
Khan spoke to CNN in December 2010 about the airstrike a year earlier that had targeted his home in Machikhel, a village in North Waziristan.
Khan said the missiles killed his 35-year-old brother, a teacher with a master's degree in English literature; his 18 year-old son, and several others. He filed a $500 million lawsuit against the U.S. government.
Khan was one of the first people to raise awareness about drone strikes, said Noor Behram, a journalist based in North Waziristan.
He said it was a great setback that he had disappeared just before he could raise the issue on an international forum during his Europe trip.
Behram said a protest against what describes as Khan's arrest would be held Tuesday at the press club in the town of Miranshah.
Muhammad Saleem reported the story from Islamabad, Chandrika Narayan reported and wrote the story from Atlanta