Police said on Thursday that the first bomb, planted under the seat of a bicycle, went off near a crowded public park near the historic Minar-e-Pakistan monument. They described the bomb as a "locally made high-intensity time device".
The explosion was triggered to hit rush hour traffic and caused a stampede by hundreds of panicked people inside the Manto Park, although none were injured.
Before the blast, hundreds of people had gathered in the park after a man had jumped to his death from a monument. But police said the suicide had nothing to do with the bombing.
Ahmad Zaidan, Aljazeera's correspondent in Islamabad, reports that the toll is expected to rise. He said some Pakistani sources suspect the hand of Indian intelligence services on the basis of previous experience with bicycle explosions, but have not made their accusation public.
About 90 minutes after the first explosion, a second bomb went off in a commercial district of Lahore, outside a jewelry shop.
Lahore police chief Tariq Saleem Dogar said the "bomb exploded near a cigarette kiosk and it triggered an explosion in a nearby fireworks shop ... four people were burned to death instantly and up to 20 people injured.
Roads were blocked off and traffic diverted, as police and explosives experts sifted through the debris for evidence.
Many in Pakistan are angry at
the president's talks with Israel
Mobin Ahmed, Lahore's security forces chief, said: "It seems the same people" are behind both attacks, but he did not say who might be behind it or their motive.
However, Information Minister Shaikh Rashid Ahmed immediately condemned the "terrorist attacks" on Friday and blamed the "enemies of Pakistan".
There has been no immediate claim of responsibility.
Wednesday night attacks
Just hours earlier, two people were injured when two bombs exploded in the town of Kalat in the restive southwestern province of Baluchistan, police said.
The first bomb went off near a gas pipeline on Wednesday evening, said local police officer Ghulam Sarwar. He said the blast caused no casualties or damage to the pipeline.
About 15 minutes later another bomb shattered windows of a telephone exchange and injured two passers-by, he said, adding that the bombs were low-intensity devices.
Police also found a packet containing about one kilo of explosive near a drain in the provincial capital Quetta.