The first blast, caused by a low intensity explosive device, went off near the Karbala Gamay Shah Imambargah or prayer ground after 6.45 pm where thousands of Shia Muslims had gathered to observe the Yaum-e-Ali. The other suicide bombers struck the nearby Bhatti Chowk area at about 7.15 pm.
Both sites are located close to the Data Darbar shrine that was recently targeted by suicide attackers. Geo News channel reported that the banned Lashkar-e-Jhangvi al-Almi had claimed responsibility for the blasts.
Lahore's District Coordination Officer Sajjad Ahmad Sajjad Bhutta confirmed that 28 people were killed in the blasts, Dunya News reported. A head of one of the suicide bombers has been recovered, police officials said.
Officials at the Mayo, Services and Gangaram hospitals told media they had received 17 bodies, including one minor girl and a policeman. Over 180 injured people were taken to the three hospitals. The Mayo Hospital alone received over 100 injured people.
At least 35 of the injured, including six policemen, were in a critical condition, officials of the state-run Rescue 1122 service said. Officials said they feared the death toll could rise further.
Provincial Law Minister Rana Sanaullah said suicide bombers were responsible for two of the blasts. Witnesses too said they had seen the bodies of the suicide attackers. The blasts triggered a stampede among members of the Shia procession that injured several persons. Angry members of the procession attacked policemen and the Lower Mall police station, saying law enforcement agencies had failed to provide adequate protection to the gathering.
A mob surrounded the Lower Mall police station and pelted stones at it. The crowd also set part of the police station and several vehicles and motorcycles on fire. Police fired teargas but were unable to disperse the mob.
Sanaullah said the paramilitary Pakistan Rangers had been called in to control the situation. He said the government would rope in clerics of all religious sects to tackle the fallout of the blasts.
The procession was making its way from the old quarters of Lahore to Karbala Gamay Shah to mark Imam Ali's death anniversary, one of Shia Islam's most respected holy men, when the blasts occurred.
In Karachi, at least seven people were injured when gunmen opened fire on a Shia procession taken out in a crowded market place. Police and the para-military rangers had surrounded the building from where some of the gunmen opened and a police official said three persons had been arrested.
The firing started when the procession was passing through Empress market in Saddar, one of the oldest markets of Karachi. This was the latest in a series of attacks targeting religious minorities and shrines in Lahore. Ninety-five members of the minority Ahmedi sect were killed in suicide attacks on two mosques in May while 45 people died when two suicide bombers targeted the Data Darbar shrine in July.
Television images of the two blast sites in Lahore showed people running helter-skelter following the explosions with some of the injured victims writhing in pain. In Karachi, City police chief Waseem Ahmed said initial investigations indicated that the firing occurred between two groups.
Tension prevailed as shops shut down in the area after the participants of the procession staged a stand-off with law enforcement agencies and demanded that the arrested men be handed over to them.
Terrorists had also targeted the Ashura and Chehlum processions of Shia Muslims last December and January evoking a strong reaction from the strong Shia population in the city.
On Ashura a suicide bomber had blown himself up in the process killing around 40 people. Prime Minister Yousuf Raza Gilani condemned the suicide blasts and said the attackers would not escape justice.