Karachi, Pakistan (Reuters) - A Pakistani peace activist has been reported missing over the weekend from eastern city of Lahore, police and one of his friends said on Tuesday. Raza Mehmood Khan, 40, a member of Aghaz-i-Dosti  (Start of Friendship), a group that works on peace building between arch-rivals Pakistan and India, hasn t been heard from since he left  home on Sunday, said Rahim-ul-Haq, a friend and an associate. He said the group has offices in both countries. Police official Shehzad Raza said Khan s family reported he had been missing since Saturday. No one has been accused in the report, he said.  We re investigating.  Several social media activists critical of the army and the country s extremists and militant groups have gone missing in Pakistan in recent months.  Four of them were released nearly a month after they disappeared early this year. Two of them - Ahmad Waqas Goraya and Asim Saeed _ later alleged in interviews with BBC and their social media posts that Pakistani intelligence abducted and tortured them in custody.      Pakistan s army has denied the accusations.         Haq said Khan spoke at a discussion on Saturday on the topic of extremism.  Everyone discussed their views and, of course, Raza was very critical,  he said.  He said that Raza s recent Facebook posts were critical of Pakistani military, especially in view of a recent sit-in protest by hard-liners that paralyzed Islamabad for over two weeks.  The extremists won almost all of their demands, including resignation of a minister they accused of blasphemy, in an agreement brokered by the army. 