US President Barack Obama has said he "profoundly" regrets the deaths of two aid workers held hostage at an Al Qaeda compound near the border of Afghanistan and Pakistan during a US counter-terror operation.
Mr Obama said he had offered "deepest apologies" to the families of American Dr Warren Eeinstein and Italian national Giovanni Lo Porto.
He also confirmed that a review had been ordered into the tragedy.
"We will identify the lessons that can be learned from this tragedy and any changes that should be made.
"We will continue to do everything we can to prevent the loss of innocent lives…in our counterterrorism operations", he added.
The United States said an American counterterrorism operation in January killed two hostages, one American and one Italian, who were held by al Qaeda in the border region of Afghanistan and Pakistan.
The operation in which American doctor Warren Weinstein and Italian Giovanni Lo Porto were killed also resulted in the death of an American al Qaeda leader, Ahmed Farouq, the White House said. Another American al Qaeda member, Adam Gadahn, also was killed, likely in a separate operation, the White House added.
In a statement, the White House expressed sorrow over the hostage deaths and said the United States had no reason to believe hostages were at the targeted compound.
Two hostages, an Italian and an American, were killed in a US counter-terror operation at an Al Qaeda compound near the border of Afghanistan and Pakistan in January, the White House has said.
The White House expressed sorrow over the deaths of American Dr Warren Weinstein and Italian Giovanni Lo Porto and said it previously had no reason to believe any hostages were at the building targeted.
In a statement, the White House added that an Ahmed Farouq, an American Al Qaeda leader, was also killed in the operation, while another US member of the militant group, Adam Gadahn, was killed in January.
Barack Obama is set to make a statement at 3pm BST
A suicide attack in Jalalabad in Afghanistan that killed at least 35 people has been claimed by the Islamic State.
A motorcycle-riding bomber attacked a bank as a crowd of soldiers and civilians gathered outside to collect their monthly salaries.
The blast killed at least 35 people and wounded 125, said Ahmad Zia Abdulzai, a regional spokesman.
The attack marks a major escalation of an affiliate of the Islamist group known as Daesh that now holds a third of Iraq and Syria in its self-declared caliphate.
In the horrific incident in Nangarhar, who took responsibility? The Taliban didn't claim responsibility. Daesh claimed responsibility for it.
Taliban spokesman Zabiullah Mujahid tweeted that the group denied and condemned the attack.
A police chief said a suicide bomb blast in Afghanistan's eastern city of Jalalabad killed 33 people and injured more than 100 outside a bank where government workers collect salaries.
Police have yet to determine if the attacker had worn the explosives or had placed them in a car. They were also investigating if there was a second explosion after people rushed to the scene to help.
An explosion in Afghanistan's eastern city of Jalalabad has killed 22 people and injured around 50, the city's police chief said.
Fazel Ahmad Sherzad said the blast took place outside a bank where government workers collect their salaries and that a suicide bomber appeared to have been responsible.
A NATO coalition soldier was killed when a firefight broke out between NATO and Afghan troops in east Afghanistan, the coalition said in a statement.
The NATO statement did not mention the nationality of the dead soldier, but Afghan police sources said the soldiers involved in the incident were American.
The shooting took place after a meeting between a senior US diplomat and a provincial governor.
Afghanistan's intelligence agency has said it foiled an attempt to assassinate Vice-President Abdul Rashid Dostum in the northerly Jawzjan province, Reuters reports.
The assassination was reportedly to have been carried out by a suicide bomber who had hidden a bomb on the back of his horse as he attended a game of buzkashi which is a national sport in the country.
"The suicide bomber ... planned to detonate it during a buzkashi match," the statement by the spy agency said.
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The US military bases in Kandahar and Jalalabad are likely to remain open beyond the end of 2015, a senior US official said as Washington considers slowing its pull-out from Afghanistan.
The anticipated policy reversal reflects the US embrace of Afghanistan's more co-operative president, Ashraf Ghani, and a desire to avoid a of collapse of local security forces as seen in Iraq.
It coincides with new efforts backed by Pakistan and China for peace talks between the Afghan government and the Taliban.