It was not possible at this stage to identify the terrorists who exploded a bomb outside Delhi High Court Wednesday killing nine people, Home Minister P. Chidambaram said.
Chidambaram told the Lok Sabha that Delhi was a target for terrorists as it was the national capital.
Accordingly, Delhi had been put on high security alert, he said in a brief statement.
The minister said the blast left nine dead and some seriously injured.
"We are clear that there is no cause that will justify the terrorist act," he said.
Major metro cities have been put on high alert.
Both houses of the Parliament was adjourned and question hour suspended after the bomb blast outside Delhi high court on Wednesday morning that left at least 9 dead and 45 injured. The Rajya Sabha was adjourned till 2pm on Wednesday
Speaker Meira Kumar condemned the bombing and expressed sympathies for victims.
She adjourned the house till 12.30 pm and said the government would make a statement later in the day.
Chariman M Hamid Ansari informed members about the explosion as soon as the house met for the day and said there may be a few casualties in the incident.
Condemning the blast, he asked the government to get details by 2pm.