Authorities in Pakistan Friday said that two back-to-back suicide bomb blasts in the country's second largest city, Lahore, killed at least 54 people, up from 45, and wounded nearly 100 others.

The increased number of dead comes as victims died of their injuries overnight.

The attack is Pakistan's deadliest this year and authorities suspect it is the work of Taliban extremists. Police reported several more minor explosions in Lahore late in the evening. But, there were no reports of casualties or major damage.

Eyewitnesses say a convoy of military vehicles passing through a busy part of Lahore was the target of the deadly attack. Most of the deaths occurred instantly and many of the victims were said to be civilians.

Local television stations broadcast a clip of the video being shot with a mobile phone just after the first blast.

The video shows a large burst of orange flame suddenly erupting in the street and people could be heard shouting "God save us! Oh my God! Oh my God!

Provincial police chief, Tariq Saleem Dogar, told reporters the bombers were on foot and they detonated their devices within seconds of each other.

The police chief says security personnel have found heads of both the attackers along with technical evidence that could help investigators.

Authorities suspect al-Qaida-linked extremists are behind the bombings. On Monday, a powerful suicide blast outside the office of a government security agency in Lahore left at least 13 people dead and more than 80 wounded.

Two days ago, a group of heavily armed militants attacked a U.S-based non-governmental organization in the northwestern Pakistani district of Mansehra, killing six people. The victims were employees of the World Vision aid group helping survivors of the devastating earthquake that struck northern Pakistan in 2005.

This week's violence in Pakistan comes after a relative lull in militant attacks across the country since the beginning of the year.

Authorities have repeatedly claimed in recent weeks that major military operations against Pakistani and foreign militants in northwestern parts of the country have broken the back of the extremists. The renewed attacks, as some top Pakistani officials put it, are a "sign of desperation" by the militants.