A suicide attack outside a court in Pakistan's capital city of Islamabad has killed at least 12 people and injured 27 more, the country's interior minister has said.

India on Tuesday strongly rejected allegations by Pakistan prime minister Shehbaz Sharif that New Delhi was behind the recent suicide bombing in Islamabad, calling the claims 'baseless and unfounded'.

The bomber tried to enter the court building on foot, but detonated the device outside, close to a police vehicle, after waiting there for 10 to 15 minutes, Naqvi told reporters at the site.