A suicide bomber targeted a Shiite Muslim mosque in northwest Pakistan on Friday, killing 21 people and wounding up to 50 as worshippers poured out of weekly prayers, officials said.

The bomber detonated explosives packed into a motorcycle in a narrow lane containing both the Shiite and a Sunni Muslim mosque in the town of Hangu, the latest bloody sectarian attack in a country where such violence is on the rise.
Pools of blood and pieces of human flesh littered the street after the attack, which also destroyed at least five nearby shops, witnesses said.
"It was a suicide attack which targeted Shiites but Sunni Muslims also fell victim since their mosque and some shops were also very close to the site," district police chief Mian Muhammad Saeed told AFP.
"We have found the head of the bomber, who came there on a motorbike," he said, putting the death toll at 21 with up to 50 others wounded, six of them in a critical condition.
Police said the bomb exploded as Shiites were leaving Friday prayers and Sunnis were going into their mosque for the main weekly sermon.
Hangu has long been a flashpoint for violence against minority Shiites, who make up an estimated 20 percent of Pakistan's population of 180 million.
It is close to Pakistan's semi-autonomous tribal belt on the Afghan border where Taliban and Al-Qaeda-linked militants have carved out strongholds.
"The Shiite and Sunni mosques are very close to each other, and the explosion took place just as Shiites were coming out of the mosque and Sunnis were going into their mosque to say Friday prayers," said police official Imtiaz Shah.
Muzammil Hussain, a 28-year-old Shiite wounded in his head and hand, told AFP that he heard the blast as he left the mosque.
"As soon as I reached the mosque exit, a huge blast rocked the area. Many people fell on me with the impact of the blast," he said by telephone from the District Headquarters hospital (DHQ) in nearby Kohat.
"I saw red and bloodied pieces of human flesh everywhere. It was a scene I'd never seen in my life before. I was half conscious when people shifted me to a local hospital from where my family took me to the DHQ," he said.
Police constable Raaz Muhammad, who took part in the rescue effort, said the blast damaged two shops selling cosmetics and three trading in vegetables.
"I could see pieces of human flesh and big blood stains on the boundary walls of the mosque and on nearby shops," he said.
"The entire street was littered with sandals and caps of the people who were coming out of the mosque," he added.
There was no immediate claim of responsibility for the attack.