A senior aide to the Afghan president and a member of the Afghan parliament have been killed in Kabul, the country's capital, in an attack claimed by the Taliban.
Jan Mohammad Khan, a former provincial governor considered an important adviser to President Hamid Karzai, and Mohammad Hashim Watanwal, the parliamentarian, died in an overnight attack on Khan's home by two gunmen wearing suicide vests, General Zahir Wardak, a defence ministry official said.
The Taliban claimed responsibility on Monday for the deaths, saying they had made Khan "pay for his deeds", according to a spokesman speaking to the AFP news agency.
The standoff in western Kabul lasted into the early hours. One of the attackers was killed before he could detonate his bomb vest, but the other blew himself up shortly after dawn, the police said.
One police officer and two assailants were also killed, the interior ministry said.
Khan moved to Kabul in 2006 after a stint as the chief administrator of the southern province of Uruzgan that was marred by controversy and corruption.
Watanwal, a former member of the communist regime, was elected to the Afghan parliament in 2005. He had reportedly returned to the country after spending the Taliban years abroad in Pakistan and the West.
"This is yet another personal blow to Karzai as Khan was from the same tribe as the president," Al Jazeera's Bernard Smith, reporting from Kabul, said.
Khan and Wantanwal are the latest in a long list of high-level Afghan officials assassinated.
Last week, Ahmad Wali Karzai, a half-brother of the president and influential chief of Kandahar's provincial council, was shot dead in his home by a close confidant.
The Taliban also claimed responsibility for Wali Karzai's killing, saying Sardar Mohamad, the assassin, had been in touch with them.
Our correspondent said Khan was also a right-hand man of Wali Karzai.
In other incidents of violence on Sunday, two NATO soldiers died in southern Afghanistan while 13 Taliban fighters were killed in an overnight strike in the east of the country, the alliance said in a statement.
The violence comes as NATO-led forces officially begin handing over control to local security forces in Afghanistan.
Bernard Smith reports from Lashkar Gah on the readiness of Afghan forces as transition looms
Sediq Seddiqi, a spokesman for the Afghan interior ministry, said the transition process was officially launched at a ceremony in the central Bamiyan province on Sunday.
All foreign combat troops are due to leave the country by the end of 2014 and Western countries have begun to announce partial reductions starting this summer, with all 33,000 US "surge" troops leaving by the end of 2012.
There are around 150,000 foreign troops in Afghanistan, nearly 100,000 of whom are from the US.
Western officials say the whole process in the seven areas, which include the cities of Mazar-i-Sharif in the north, Herat in the west, and Lashkar Gah in the south, could take up to two years to implement.
But widespread doubt remains over the ability of the Afghan security forces to take full responsibility for warding off attacks, amid high levels of illiteracy and attrition within the army and police.
Waliullah Rahmani of the Kabul Centre for Strategic Studies said the killings will have "quite the negative effect on the establishment," considering that it is currently "a very vital time for Afghanistan".
"We are officially entering into a transition process that will put the burden of all security issues on the Afghan forces, which is widely welcomed by the Afghan government," Rahmani told Al Jazeera.
"There are fears from the Afghan people [over] whether this process will be successfully handed over to the Afghan security officials."
Daoud Sultanzoy, an Afghan analyst and former member of the parliament, told Al Jazeera: "The drawdown is, unfortunately, a foregone conclusion and it's based on political decision-making, political calendars, rather than the situation on the ground."
Phyllis Bennis, a fellow at the Institute for Policy Studies in Washington, said the assassination of Khan could be the Taliban's way of sending a message to the US.
"Jan Mohammad Khan was known to have close ties with the US and was alleged to have been involved in working with the US on some of the military's night raids - which have become such a flash point among Afghan civilians because they have led to so many civilian casualties," Bennis told Al Jazeera.