At least nine people have been killed by two suspected suicide blasts at a Sufi shrine in the Pakistani city of Karachi, say officials.
Two children were among those killed and some 55 people were injured, a senior police official told the BBC.
The blasts hit the busy Abdullah Shah Ghazi shrine in Clifton district as people were leaving evening prayers.
Pakistan's President Asif Ali Zardari has condemned the incident "in the strongest possible terms".
A spokesman for the Taliban told the BBC it had carried out the attack.
Eyewitnesses said the blasts hit close to the entrance to the shrine on its busiest night of the week, when people had gathered to distribute food to the poor.
"I saw this boy with long hair. He was coming into the shrine when he blew himself up," one witness told the BBC.
Babar Khattak, the top police officer in Sindh province, said the blasts happened about 10 seconds apart, close to a metal detector checking people entering the mosque.
Mohibullah Khan, 38, said he heard a "huge bang" before smoke billowed from the area.
"I ran back toward the mosque and seconds after heard another big explosion. Then I moved to help the wounded and put six or seven of the crying ones in ambulances and police vehicles," he told the Associated Press news agency.
Gul Mohammad was in the street when he heard the explosions and said he ran inside to help the victims.
"Some bodies were lying on the ground and several people wounded in the blasts were crying in pain. Then ambulances started arriving and moving the injured to hospitals," he told the AFP news agency.
The BBC's Shoaib Hasan at the scene said crowds of people gathered outside the shrine awaiting news of loved ones as the clean-up operation began.
Dozens of security force members were also at the scene and there was blood spattered on the pavements, said our correspondent.
The Sufi community in Karachi has declared three days of mourning, during which all Sufi shrines in the city will be closed.
Security is also being tightened at mosques and other sensitive areas in Karachi, said officials.
Sindh's provincial Home Minister Zulfikar Mirza said the shrine had "the best available security" but that "humanly, it is not possible to stop suicide bombers intent on exploding themselves".
In a statement, Mr Zardari blamed the attacks on "those who want to impose an extremist mindset and lifestyle upon our country" but said the government would not be deterred.
"We remain committed to fighting these murderers and expelling them from our land," he said.
Pakistan has seen a significant rise in suicide bombings in recent years.
The Karachi blast appears to echo a double suicide attack on another Sufi shrine in Lahore in July.
More than 40 people were killed and nearly 200 injured in that incident, which targeted the popular Data Darbar shrine.