US Secretary of State Hillary Clinton has said the militant attack on Pakistan's army headquarters served to underline the extremist threat to the Islamabad government.
Clinton, who arrived in London late on Saturday as part of her five-day European tour, said the measures being taken to root out extremists in Pakistan were "very important".
The top US diplomat told reporters she had been briefed about the attack.
She said she wanted to "point out this shows the continuing threats to the Pakistani government and the very
important steps that the civilian leadership, along with the military, are taking to root out the extremists and prevent
violence and direct assaults on the sovereignty of the state."