Imran Khan, Al Jazeera's correspondent in Rawalpindi, said: "Hundreds of people were at the bank at the time, which explains why the death toll has risen so sharply in the last couple of hours.
"When this blast took place, the noise was so loud, one witness said she felt as if her whole world had ended. Another said she saw a woman lying on the street missing half her body - very harrowing stories at the scene of this bomb blast.
"This is a highly secure area. Just a couple of weeks ago there was a siege that took place on the army headquarters. The question already being asked is how another bomb blast could take place in such a sensitive area.
"There are no claims of responsibility so far."
Hours later, two bombers detonated their explosives when stopped at a police checkpoint on the outskirts of the Punjabi city of Lahore. At least seven officers were hurt, two of them seriously.
Police said the amount of explosives in the vehicle would have caused serious loss of life had it been driven into the heart of the city.
A surge in violence has hit Pakistan in recent weeks, leaving more than 300 people dead last month alone as the military launches a major offensive against the Tehreek-e-Taliban (TTP).
Pakistani troops have been locked in street battles for two days with Taliban fighters in Kanigurram, one of the largest towns in South Waziristan and described as a major operation centre for the TTP.
The worsening security situation coincides with a UN decision to pull out international staff from Pakistan's northwest.
Monday's announcement follows the deaths of more than 100 people in a car bombing in Peshawar, the main city of the North West Frontier Province (NWFP), on October 28.
Ishrat Rizvi, a UN spokeswoman, told the AFP news agency that the UN employees "will be relocated immediately". He was unable to say how many the decision affected.
Ban Ki-moon, the UN secretary-general, said in a statement that the world body had raised the security level to "phase four" in NWFP and the Federally Administered Tribal Areas.
"The decision has been taken bearing in mind the intense security situation in the region," the statement said.
Last month, the UN's World Food Programme closed distribution centres serving more than two million people in the northwestern region because of security fears.
Against this backdrop of violence and tensions, the Pakistani authorities have offered a reward worth $5m for information leading to the capture, dead or alive, of Hakimullah Mehsud, the leader of the TTP, and 18 other fighters.
|Pakistan has offered a $5m reward for the capture of Mehsud and 18 others [AFP]
The reward for the group's senior fighters was offered in a government advertisement on the front page of The News daily and on Pakistani television channels overnight.
"The activities of these brutal people, who have no fear of God, are bringing a bad name - not only to the Mehsud tribe but all tribesmen ... and also give a bad name to Pakistan in the whole world," the advertisement said.
"These people certainly need just punishment. They are the killers of humanity. Help the government of Pakistan to annihilate them."
Mehsud, who took on the leadership mantle after a US drone attack killed his predecessor, Baitullah Mehsud, in August, headed the list with 50 million Pakistan rupees ($600,240) on his head.
The TTP has been blamed for some of the worst attacks in Pakistan, which have killed about 2,400 people in a wave of violence over the past two years.