Anti-aircraft guns have been installed and nearly 300 additional security personnel deployed at a prison in Rawalpindi where Mumbai terror suspects are being held following intelligence reports that militants might try to free them.

Zakiur Rehman Lakhvi, operations commander of the banned Lashker-e-Taiba, and four other LeT operatives - Zarar Shah, Hamad Amin Sadiq, Abu al Qama and Shahid Jamil Riaz - are currently being held at Adiala Jail in Rawalpindi after their arrest for alleged involvement in planning and executing the Mumbai attacks.

Authorities have tightened security by deploying about 300 additional personnel from the Pakistan Rangers, Punjab Constabulary and Elite Force inside and outside the jail.

Anti-aircraft guns have been installed on the rooftop of the prison to foil any possible jailbreak attempt, unnamed interior ministry officials were quoted as saying by 'The News' daily.

The officials said 25 armed personnel of the Pakistan Rangers, 75 from the Punjab Constabulary and 85 Elite Force personnel had been deployed for patrolling around the jail round the clock.

Over 100 additional Pakistan Rangers personnel have been deployed in the jail to beef up security.