Karachi, Pakistan - Two bombs in the Pakistani city of Karachi have killed at least 22 people and injured more than 50.
In the first blast, a motorbike laden with explosives hit a bus carrying Shia Muslims to a religious procession and exploded, killing 12 people.
An hour later, another bomb exploded outside the entrance to the emergency ward of the hospital where the victims of the first attack were being treated.
At least 10 people were killed in the second attack.
The bombings happened in spite of tight security across Pakistan.
Forty days ago, during the last major Shia festival, a suicide bomber killed 25 worshippers in the city.
Shia Muslims are marking the end of the Arbaeen religious festival, with Friday being the final and most important day of 40 days of mourning for the Prophet Muhammad's grandson.
Also on Friday, at least Shia Muslims were killed in the Iraqi city of Karbala as they took part in a major Arbaeen event.
Approximately a million Shia Muslim pilgrims are in Karbala to visit the Imam Hussein shrine at the end of commemorations.
Sectarian tension
In Karachi, the first attack took place on a commercial street near the main Sharah-e-Faisal road connecting Karachi airport with the city.
The bus that came under attack was one of dozens used to transport Shia pilgrims from all over the city to a central procession.
It was not clear whether the motorcycle bomb was rammed into the bus by a suicide bomber or was parked by the side of the road.
The attack injured about 50 people, who were taken to Jinnah hospital.
About an hour later there was a large blast just outside the emergency ward of the hospital.
The BBC's Jaffer Rizvi, who was at the hospital at the time, says police suspect a suicide bomber was responsible for the second explosion.
When the blast went off, there was a huge panic inside the hospital, he says. Hundreds of people mourning those killed in the first attack had gathered there and were shouting slogans condemning both militants and the government.
Police officer Ghulam Nabi also told Reuters news agency another bomb had been defused after being discovered inside a TV set on the hospital premises.
Sectarian tension between the Shia minority and the Sunni majority rose after the December attack, and riots erupted.
Tension remains high, and paramilitary troops were deployed in the city days ago amid deadly clashes between rival political groups.
The Shia-Sunni schism originates from a dispute soon after the death of the Prophet Muhammad over who should lead the Muslims.
Sunnis remain the majority globally, with Shias estimated to number about 10% of all Muslims.