A special service of commemoration will be held to mark the end of the combat mission in Afghanistan, Prime Minister David Cameron has told MPs.
The event will take place at St Paul's Cathedral on March 13.
A drone attack by US forces has killed at least six suspected militants in north west Pakistan, intelligence officials have said.
The strike hit compounds in Lawara Mandi, near the border with Afghanistan, killing between six and nine suspected militants.
It comes as Pakistani officials debate plans to intensify a crackdown on Taliban insurgents behind the massacre of 132 schoolchildren last month.
At least 20 civilians were killed and many more were wounded when mortar rounds hit a wedding party in Afghanistan's volatile southern Helmand, the scene of fighting between the army and the Taliban.
General Mahmoud, the deputy commander of the Afghan 215 corps in the province, said artillery was fired from three directions at a village in Sangin district where the wedding was held on Wednesday.
"What we know so far is that our soldiers fired mortar rounds from three outposts but we do not know whether it was intentional," Mahmoud told Reuters.
"We have launched our investigation and will punish those who did this."
Gul Pasha Bakhtiar, deputy provincial police chief, said 26 civilians, including women and children, were killed and 41 wounded by mortar shells fired from the army side.
The U.S.-led coalition in Afghanistan also known as the International Security Assistance Force (ISAF), formally ended its combat mission on Sunday with a ceremony held in secret due to the threat from the Taliban.
About 13,000 foreign troops, mostly Americans, will remain in the country under a new, two-year mission named "Resolute Support" that will continue the coalition's training of Afghan security forces.
In a statement US President Barack Obama said: "Now, thanks to the extraordinary sacrifices of our men and women in uniform, our combat mission in Afghanistan is ending, and the longest war in American history is coming to a responsible conclusion."
The Prime Minister and the Leader of the Opposition praised the courage of Britain's armed forces in a Christmas message to troops.Read the full story ›
A policeman has been killed and two others injured in a suicide bomb blast on the outskirts of Afghanistan captial Kabul.
Interior ministry spokesman Sediq Sediqqi said a patrol car was sent to a village near the airport after reports a bomber was trying to enter the city in a car laden with explosives.
But they were able to detonate the bombs before the officers could stop them.
Several Afghan soldiers have been killed after a suicide bomber destroyed a bus in the capital Kabul.
At least six soldiers were killed in the attack, which left a column of black smoke above the city.
It comes shortly after a number of other Taliban attacks as violence intensifies in the country ahead of the withdrawal of most international troops in the next fortnight.
Earlier, a senior Supreme Court official was shot dead as he left his home.
Last night, two foreign soldiers were killed in an attack on a Nato convoy nearby.
Two soldiers in a Nato convoy have been killed by a Taliban bomb in Afghanistan.
The attack near the Bagram airfield base north of Kabul is the latest in a spate of deadly attacks in and around the capital as international forces leave the country.
Both soldiers were from the United States, the Associated Press news agency reports.
A suicide bomb attack at a school in Afghanistan has left at least one person dead and 16 others injured.
General Ayoub Salangi, the country's deputy interior minister, said the 17-year-old bomber wore an explosive vest inside the venue and detonated it during an event at a French-run high school in the capital city Kabul.
Defence Secretary Chuck Hagel has announced the US will delay the withdrawal of up to 1,000 troops from Afghanistan.
Speaking at a press conference in the Afghan capital Kabul, Hagel said:
"10,800 troops, rather than 9,800, could remain in Afghanistan through the end of this year, and for the first few months in 2015."
"#POTUS' authorization will not change our troops’ missions, or the long-term timeline for our drawdown."
"The international community must not waver in its support for a stable, secure, and prosperous Afghanistan." http://t.co/8tfwZhjVHW