The Pakistan-based Harkat-ul-Jehadi Islami (HuJI) has claimed responsibility for the terror bombing outside the Delhi High Court complex Wednesday.
In an email sent from an unknown location to various media houses, the HuJI claimed that the blast which left 10 people dead was the handiwork of the terror group, which also an affiliate in Bangladesh.
It demanded that the death sentence of 2001 parliament attack convict Afzal Guru should be immediately "repealed".
Official sources said that the home ministry has not ruled out the involvement of the group in the blast.
Guru has been sentenced to death by the Supreme Court after he was convicted for the Dec 13, 2001 parliament attack.
The Jaish-e-Mohammed militant has filed a mercy petition with President Pratibha Patil. The decision on his clemency is pending, even as the home ministry has recommended it be rejected.
"We are taking the email seriously," National Investigation Agency (NIA) chief S.C. Sinha told reporters.