Nine people were killed and nearly 45 injured in a blast outside one of the entry gates to Delhi high court on Wednesday morning.
"I have heard the sad news from Delhi. This is a cowardly act, but we will deal with it. All political parties must come together to fight the scourge of terrorism," he said.
"My heart goes out to those who have perished in the blast and my best wishes to those who were injured. This is a long war against terrorism and we can't fight it alone," he added.
When queried on the suspected outfits behind the blast, the prime minister said it was "too early" to pinpoint which terror organisation was behind the blast. Dr Singh added that he had already spoken to Home Minister P Chidambaram about the blast.
National Security Advisor Shiv Shankar Menon, who is accompanying the PM, refused to comment on the blast.
