The attacker and his accomplice were detained.
Tunda was arrested by Delhi Police last week from the India-Nepal border.
Shiv Kumar Raghav, 40, slapped Tunda at around 3.50 p.m. when the terrorist was being taken to a court after three days of police custody.
Along with Raghav, another member of Hindu Sena, Vishnu Gupta, was also detained by police just after the attack.
"Tunda is a traitor, he should be hanged," Raghav was shouting after he slapped Tunda and was detained by police.
Police personnel have been reinforced outside Patiala House court after the incident.
--IANS (Posted on 20-08-2013)