Islamabad, Pakistan (CNN) -- The Pakistan Taliban claimed responsibility Thursday for a series of bombings a day earlier that left dozens dead, primarily Shiite Muslims gathering for a revered religious mourning period.
At least 31 people were killed and 68 wounded in the blasts Wednesday that came amid heightened security over the Shiite observance, which has been targeted in recent years by extremists.
The attacks also came as leaders of Muslim nations gathered in Islamabad for the Thursday start of an economic summit of the Developing 8 or D-8.
Of the blasts, the deadliest was in Rawalpindi where a suicide bomber joined a Shiite processional, police official Shahid Hussain said. At least 23 people were killed and 35 wounded in the explosion, he said.
Pakistan Taliban spokesman Ihsanullah Ihsan claimed responsibility for the attacks in Rawalpindi, Karachi and Shangla.
In Karachi, at least two were killed and one wounded in a double-bombing that targeted a Shiite community center, a police official said.
In northern Pakistan's Shangla, at least one person was killed and four wounded when a blast targeted a police vehicle, officials said.
There was no immediate claim of responsibility for a blast in Quetta that also appeared to target Shiites. At least five people were killed and 28 wounded when a bomb detonated in a predominantly Shiite neighborhood, said Wazir Khan Nasar, a police official.
Ihsan said the Pakistan Taliban targeted Shiites taking part in mourning observances because they believe it denigrates the Prophet Mohammed.
The Taliban attacks came during the holy month of Muharram, which culminates Saturday with the height of the mourning period.
The Shiite observance commemorates the death of the Prophet Mohammed's grandson, who was killed in the Battle of Karbala in 680 AD. The battle and subsequent death of Imam Hussein caused the split between Shiite and Sunni Muslims.