The latest explosion appeared to have been a bomb planted in a parked car and detonated by remote control, said police officer Zahid Khan. It went off in a crowded market that is the city's oldest bazaar near a mosque and a police station, officials said.
The blast damaged the mosque and nearby shops and caused many vehicles to go up in flames, said police officer Nawaz Khan.
The city's top government official, Sahibzada Anees, said 37 had died while 75 were under treatment at the city's Lady Reading Hospital.
Such attacks in Peshawar, which is the provincial capital of Khyber Pakhtunkhwa province, have claimed over 130 lives since last Sunday when two suicide bombers blew themselves up in a crowd of worshippers at a church, killing 85 people.
Then on Friday 19 people died when a bomb planted on a bus carrying government employees home for the weekend exploded in the Peshawar outskirts.
The bomb that went off Sunday was some 300 meters (yards) from the All Saints Church, which was the scene of last Sunday's carnage.
A book shop owner, Nazar Ali, had just opened his shop when the bomb went off.
"It was a huge blast that was followed by fire in vehicles. Thick black smoke covered the air and splinters spread all over. I saw people lying dead and bleeding all over," he said.
Many of the old buildings used in the historic Qissa Khawani market are constructed from wood which easily caught on fire when the bomb went off, said senior police officer Shafqat Malik.
Another man was shopping for breakfast when the bomb exploded.
"Suddenly there was a huge bang and I fell on the ground," said Adnan Hussain, speaking from the hospital. "My cousin Rizwan is dead and the other is critical."
One man at the hospital said that 13 members of a single family were among the dead. Mohammad Alam said that they had come to Peshawar from a nearby village to invite him to their son's marriage. He said they were in a van near the station when the bomb exploded.
There was no immediate claim of responsibility. The Sunni militant group Jundullah claimed responsibility for the church attack, saying it targeted Christians to avenge the deaths of Muslims killed by U.S. drone strikes.
The new government of Nawaz Sharif has said it would like to negotiate with Pakistan's largest militant group, the Taliban, to end the bloodshed, but so far those efforts have made little progress and attacks like Sunday's have continued.
On Saturday, a spokesman for the Taliban criticized Sharif, saying comments by Sharif saying the militants must lay down their weapons and respect the constitution indicated the new leader is not serious about peace talks. Previously Sharif had not given preconditions for the talks.
"By telling us that we will have to lay down arms and respect the constitution, the prime minister, Nawaz Sharif, showed that he is following the policy of America and its allies," the spokesman said. "We will hold talks with (the government) only when it gets the real power to take decisions."
Also in northwestern Pakistan, two missiles from an American drone hit a compound in North Waziristan Sunday, killing three militants affiliated with the Punjab province branch of the Pakistani Taliban, said two intelligence officers. They spoke on condition of anonymity because they were not authorized to speak to the media.
Associated Press writer Rasool Dawar contributed to this report.