ISLAMABAD - At least 20 soldiers were killed and 25 others injured in a suicide bomb attack on security forces' convoy in Pakistan's northwestern district of Bannu on Sunday morning, local media reported.

Security sources said that a suicide bomber detonated his explosive-laden vehicle amid the convoy of security forces in cantonment area of Amandi town in Bannu district.

The bodies and injured were admitted to the nearby Combined Military Hospital.

The death toll may further rise as some of the injured were in critical condition.

The blast took place in one of the civilian vehicles hired by the Frontier Constabulary (FC) for their weekly movement from Bannu to northwestern restive tribal region of North Waziristan.

Security forces cordoned off the area and launched an investigation into how an explosive-laden vehicle succeeded in joining the convoy.

The huge blast that was heard miles away destroyed many other vehicles of the convoy.

No group has claimed responsibility for the attack yet.

Pakistani president Mamnoon Hussain and Prime Minister Nawaz Sharif condemned the incident.