US President Barack Obama has condemned as "outrageous" Saturday's deadly suicide bomb attack on a town in north-western Pakistan.
A female bomber killed at least 43 people in the attack on a large crowd receiving food aid in Khar in the Bajaur region.
The town is in tribal areas close to the Afghan border - a Taliban and al-Qaeda stronghold.
People displaced by fighting had been getting food at a distribution centre.
Saturday's bombing was the latest in a string of recent attacks in Pakistan's north-west.
"I strongly condemn the outrageous terrorist attack in Khar, Pakistan," President Obama said.
"Killing innocent civilians outside a World Food Programme distribution point is an affront to the people of Pakistan, and to all humanity," he said.
"The United States stands with the people of Pakistan in this difficult time, and will strongly support Pakistan's efforts to ensure greater peace, security and justice for its people."
The UK government has also condemned the attack, along with the Pakistani government.
UK Minister for South Asia Alistair Burt said: "This appalling attack on innocent refugees is a cruel reminder of the indiscriminate aims of the terrorist and an example of why the world must work together to do all we can to confront a menace without boundaries."
Pakistani Prime Minister Yusuf Raza Gilani said those responsible had no regard for humanity or religion, and that the fight against militants would continue.
Pakistan's Taliban said they ordered the attack on the distribution centre, which is used by the World Food Programme and other aid agencies.
They said the rebels had targeted the local people - displaced members of the Salarzai tribe - because of their support for the Pakistani military.
An estimated 300 people were queuing for food at the time of the blast, with reports saying at least 100 people were injured in the bombing.
The tribal district of Bajaur, where the attack took place, has seen several military operations to clear it of insurgents.
The army had previously declared the operations a success and the area safe for the displaced to return to.
The attack also came as Pakistan's military took action against militants in Mohmand, an adjacent tribal region, killing an estimated 40 rebels.