Afghan president Hamid Karzai is moving to replace the country's intelligence chief and the ministers of defence and interior.
The planned reshuffle is the first step in what senior government officials said was a planned wider cabinet shake-up aimed at solidifying the president's power before elections and the drawdown of foreign forces.
Mr Karzai is also trying to shore up his shaken security team as his administration struggles to build an army and police force in the face of a resurgent Taliban as the US and other foreign forces begin to withdraw.
The coalition's training efforts have increasingly become a target for insurgents - Nato said yesterday that three more of its service members were killed in the latest in a string of attacks by Afghans on international trainers.
The troops were killed by a man in an Afghan army uniform who turned their gun on them on a Nato base in southern Afghanistan.
US defence sources said the shooting took place in Uruzgan province, where the only non-American coalition forces are Australian.
The Australian Defence Force said today that Australian soldiers had been killed in an incident in Afghanistan, but did not say how many and was waiting to notify the soldiers' families before giving further details.
Mr Karzai's latest reshuffle of top officials - if it goes through - appeared to be an attempt to stack the cabinet and electoral commission with his allies in a bid to retain power behind the scenes after his final five-year term ends and the international troops withdraw in 2014.
"With the elections coming, with the transition ... it is a time for him to restrengthen his team," said Martine van Bijlert, an expert at the Afghan Analysts Network. "I think we could be seeing a major reshuffle. ... The question is always: can he make it stick?"
An Afghan official close to the president's office said the head of the country's election commission, the attorney general and the finance minister were expected to be among the top positions included in the shake-up.
Nothing is final until there is an official announcement from Mr Karzai and the president could still change his nominees or leave the government largely untouched. But Ms van Bijlert noted that while rumours of cabinet shake-ups are common, Mr Karzai may use the window provided by the parliament's sacking of his defence and interior ministers to make wider changes.
However, any changes must be confirmed by parliament, and it is unclear whether Mr Karzai would be able to muster the necessary support from MPs, many of whom feel the president too often ignores parliament's constitutional powers to push his nominees through.
There are already grumblings about some of the names that have emerged.
Two senior Afghan officials said Assadullah Khalid, the minister of tribal and border affairs, would replace Rahtamullah Nabil as the head of the National Directorate of Security - the country's main spy agency. Mr Khalid, a former governor of two provinces, has been criticised for alleged human rights abuses and could be a controversial pick.
A statement from Mr Karzai's office yesterday said Mr Nabil would step down because he had finished his two-year term. It did not name a replacement.
Mr Karzai also plans to name Bismullah Khan Mohammadi, who was ousted from his post as interior minister earlier this month by parliament, as defence minister, and Mushtaba Patang, an ex-police chief in the country's north, as the new interior minister, according to Abdul Qadir Qalatwal, an MP from Zabul province.
He said the president's office had notified parliament of the names.
A spokesman for Mr Karzai, Hamid Elmi, confirmed that the president would send nominees for the defence and interior ministers, as well as for a new intelligence chief "in the near future", but he would not confirm the names.
The planned swap of the three key security officials raised questions of stability in the administration as the Afghan government struggles to build a 352,000-strong army and police force by the end of the year that can fight the Taliban, a centrepiece of the withdrawal strategy for the US and its allies.
Despite some reports of improved Afghan security performance, violence continues to spiral across the country.
Nato spokesman Jamie Graybeal said the coming changes would not slow progress towards building the Afghan security forces, saying the coalition's relationship with the Afghan government "reaches across various levels of the ministries and will guarantee our strategy for transformation will remain on track".
The US has spent $22bn (€17.5bn) on the training effort that has been plagued with pitfalls, including an alarming number of US and allied deaths by Afghans who turned their weapons on their international counterparts.
There have been at least 34 such attacks so far this year, killing 42 coalition members, mostly Americans.