At least 40 people have been killed and 30 others injured in a bomb blast occurred in a mosque during Juma prayer in Hayagai Shari area of Upper Dir , a private TV channel reported here Friday citing a foreign news agency. According to the channel, the bomb went off when near 400 faithfuls were offering Jumma prayer in the mosque. Nature of the blast is yet to be identified however, officials claimed that the bomb was planted in the mosque and was detonated by a remote control device. Some eyewitnesses claimed that the blast was suicidal.