A bomb exploded outside New Delhi's High Court on Wednesday, killing at least 11 people and injuring 66, in an act of suspected terrorism in the heart of India's capital that further heightened concerns about the nation's security vulnerabilities.

The high-intensity blast occurred at 10:14 a.m. near the courthouse reception area. Officials said they believed the bomb was placed in a briefcase.

Addressing reporters in Bangladesh, where he has been visiting, Prime Minister Manmohan Singh said, "We will never succumb to pressure from terrorists. All political parties must unite to crush the scourge of terror."

Indian news channels said the Islamist militant outfit Harkat-ul-Jihad al-Islami had claimed responsibility for the attack in an email to media organizations. But Home Minister P. Chidambaram told Parliament the government has not yet identified the group responsible for the blast. He said investigative teams from the central government and New Delhi police are initiating a probe.