A suicide bomb attack on a luxury hotel in the north-west Pakistani city of Peshawar, has killed 15 people and injured at least 60.
Gunmen stormed the outer security barrier at the Pearl Continental Hotel before blowing up a vehicle containing, police say, 500kg of explosives.
Two foreign citizens - both UN workers - were killed and several were injured.
A series of bombs have hit cities, including Peshawar, since a government crackdown on Taliban militants.
Jill McGivering, BBC News
The PC is a well-known landmark in Peshawar. Often used by foreigners but also by Pakistani officials and businessmen, it is known for good Western as well as local food and 5-star service. All factors which may have contributed to its becoming a target.
When I visited recently, there was a whole series of security checks. First of vehicles, as they drove in, past heavy concrete barriers. Then of people, screened by metal detectors and bag searches.
But suicide bombers and gunmen are hard to stop. There are clear echoes of the devastating assault on the Marriott Hotel in Islamabad last September.
Security in Peshawar has worsened dramatically in the last year. Many of those who can afford to move have taken their families to Islamabad or beyond - abandoning a city now becoming consumed by fear and violence.
Peshawar, the main city in the country's north-west, is not far from the Swat valley, where the government offensive has been concentrated.
Pakistani Prime Minister Yusuf Raza Gilani swiftly condemned the attack but the blast hardly comes as a surprise, says the BBC's Chris Morris, in Islamabad.
While there was no immediate claim of responsibility for Tuesday night's attack on what is the most prominent hotel in Peshawar, our correspondent says most people will assume it to be the work of the Taliban.
A symbol of Peshawar's contact with the rest of the world, a place where government officials and foreign dignitaries are accustomed to staying, has been attacked, he adds.
The attack killed a Serbian UN refugee agency worker and a Unicef worker from the Philippines.
The injured include a British man and a German national, Peshawar district coordination officer Sahibzada Anis said.
At least a dozen UN employees were staying at the hotel at the time of the explosion.
UN Secretary-General Ban Ki-moon spoke of "a heinous terrorist attack which no cause can justify".
'Shouting and running'
Eyewitnesses told the BBC News website the blast could be seen up to 5km (3 miles) away. The blast left a large crater and parts of the hotel were destroyed.
I saw the red light from there blowing and then I heard a huge sound
Three men riding in a truck approached the main gate of the hotel and opened fire at security guards before driving inside, police official Liaqat Ali told AP, quoting witness accounts.
"They drove the vehicle inside the hotel gates and blew it up on reaching close to the hotel building," he added. Ali Khan, a hotel waiter, said he had been working when the attack happened.
"I was in the Chinese restaurant when we heard firing and then a blast," he told Reuters news agency. "It was totally dark and people started shouting and running."
An injured man, Jawad Chaudhry, said he had been in his room on the ground floor when he heard gunshots, then a big bang.
"The floor under my feet shook," he said. "I thought the roof was falling on me. I ran out. I saw everybody running in panic. There was blood and pieces of glass everywhere."
Musa Khan, a BBC News website reader in Peshawar, said he was far away when the blast happened but could tell it was "huge".
"I was in the university lawn with my friends," he said. "I saw the red light from there blowing and then I heard a huge sound."
Another Peshawar reader, Imran, said window panes 5km away had been shattered while a third, Samee Uddin, reported gunshots and then a "huge cloud of smoke [which] could be seen from more than 3km away".
The Pearl Continental, usually just called the PC, is a well-known landmark in Peshawar, often used by foreigners, Pakistani officials and businessmen.
Correspondents say it runs a series of security checks, first of vehicles as they drive in past heavy concrete barriers, then of people who are screened by metal detectors and bag searches.
Government forces launched an offensive earlier this year to crush a Taliban-led uprising in the Swat valley aimed at enforcing Sharia law.
Taliban leaders have promised to launch revenge attacks on major Pakistani cities and claimed a bombing in Lahore last month which left at least 28 people dead.
A devastating suicide bomb attack on the Islamabad Marriott hotel last September killed at least 53 people and injured more than 266.
Fidayeen-e-Islam, a little-known Pakistani militant group, told the BBC it had carried out the attack with the aim of stopping US interference in Pakistan.
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