A spokesman for the Jamaat-ul-Ahrar, an offshoot of the Pakistani Taliban, has given an interview to America's NBC News.
In it he identifies Salahuddin Khorasani as the man who blew himself up at a Christian festival in a Lahore Park on March 27.
He said the attack was targeted at Christians, although most of the dead were Muslim. More than 320 others were injured.
The militant promised more attacks on Pakistan's Christian community which is already under pressure from a growing Islamist agenda.
Jihadis were training in Afghanistan with the mission of crossing the border to target Christians, he said.
Pakistan has been increasing operations against terrorists across the country since the Easter attack.