By Mubasher Bukhari LAHORE, Pakistan (Reuters) - Pakistani authorities on Monday hunted members of a Taliban faction which once declared loyalty to Islamic State after the group claimed responsibility for an Easter suicide bomb targeting Christians that killed at least 70 people. The brutality of Sunday's attack by Jamaat-ul-Ahrar, the group's fifth bombing since December, reflects the movement's attempts to raise its profile among Pakistan's increasingly fractured Islamist militants. At least 29 children enjoying an Easter weekend outing were among those killed when the suicide bomber struck in a busy park in the eastern city of Lahore, the power base of Prime Minister Nawaz Sharif.