Death toll rises in twin bombing in Pakistan

The second bomb was detonated outside the emergency room of Jinnah Hospital, Karachi, on February 5, 2010.

STORY HIGHLIGHTS

The first explosion targeted Shiite religious observers on a bus
The second attack occurred outside a hospital treating victims of the first blast
Motorcycles were used in both attacks, say officials
A blast in Karachi in late December, during Ashura, killed more than 40 people

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Pakistan

Islamabad, Pakistan (CNN) -- The death toll has risen to 33 in Friday's twin blasts in Karachi, authorities said Saturday.

One blast targeted a bus filled with Shiite religious observers, killing scores. Another explosion in front of a hospital where attack victims were being treated, a government official said.

Along with the the deaths from both blasts, more than 160 people were injured, the government official said.

Motorcycles were used in both assaults, police said, and they came during the Shiite observance of Arbaeen, which takes place 40 days after the anniversary of Iman Hussein's death, also known as Ashura.

Along with the fatalities, 69 people were injured in the first blast, said Dr. Saghir Ahmed, Sindh provincial health minister.

The second blast happened in front of the emergency room at Jinnah Hospital, where doctors treated people from the first attack and others on stretchers were waiting to be taken to the crowded facility. Along with the 13 killed, 92 were injured.

The last deadly blast in Karachi was in late December during Ashura, when more than 40 people were killed.

-- CNN's Nasir Habib contributed to this report