As many as ten people have been killed in New Delhi following a bomb attack on the Indian High Court.

A further 61 people are believed to have been injured in what Indian prime minister Manmhan Singh branded a “cowardly act”.

Extremist group Harkat-ul Jihad al-Islami (Huji) claimed it has planted the bomb – which was left at the first check point into the court – in an email delivered earlier.

However, Indian officials have yet to confirm who was responsible.

The Unites States state department has previously said Huji is a terrorist organisation with links to al-Qaeda.

Prime minister Singh condemned the attack.

Speaking from Bangladeshi capital Dhaka, where he is on a state visit, he said: “This is a long war in which all political parties, all the people of India, have to stand united so that this scourge of terrorism is crushed.

In June, a bomb exploded in a car outside the same Delhi court complex. There were no casualties on that occasion.

“British nationals are advised to monitor local media and be more vigilant around government buildings and public places,” warned a statement from the British Foreign & Commonwealth Office (FCO).

“There is a high threat from terrorism throughout India. Recent attacks have targeted public places including those visited by foreigners.”