A high-level United Nations delegation is in Afghanistan to underline support for the country's leader, Hamid Karzai.
Warlords are urged to unite behind Hamid Karzai's administration
The team - including representatives from all 15 members of the UN Security Council - has met Mr Karzai at the beginning of the trip.
They are due to travel to key cities to urge powerful provincial commanders to co-operate with the government.
Increasing violence and a rise in drug production are posing strong challenges to Mr Karzai's administration.
Two civilians were killed on Sunday in clashes between rival militias.
The woman and child died during fighting in the northern Sari Pul province, said General Abdul Sabor, a commander under Tajik warlord General Atta Mohammed.
At least five fighters were also killed - two from the Tajik faction, and three from ethnic Uzbek warlord General Abdul Rashid Dostum's forces.
There have been repeated outbreaks of factional fighting between soldiers loyal to the two leaders.
General Dostum used to be the undisputed power broker in the north, but Atta Mohammed's influence has grown since the Tajik-dominated Northern Alliance took over Kabul after the fall of the Taleban.
The UN delegation plans to meet both commanders, to impress upon them the international community's support for President Karzai's transitional administration.
A spokesman for the Afghan Government described the visit as "an historic one".
The fact that all 15 members of the Security Council had travelled to Afghanistan pointed to the importance the UN attached to the country, he said.
The mission will try to boost support for the peace process
Germany's UN ambassador Gunter Pleuger - who is leading the week-long mission - said his delegation wanted to reassure Afghanistan that it remained "high on the agenda of the Security Council".
"The Security Council and the international community support the reconstruction process in the country," Mr Pleuger said.
He said his team would urge faction and provincial leaders to co-operate fully with Mr Karzai's government to implement the Bonn agreement that ended the war, as the country prepares for elections next year.
There has also been a resurgence of the Taleban in the largely Pashtun south.
More than 300 people, including Taleban fighters, have been killed in violence across the country since the beginning of August.
The UN trip takes place after the UN Security Council unanimously voted to expand the more than 5,000-strong Nato-led peacekeeping force beyond the capital, Kabul.
Mr Karzai's government has tried to curb the influence of regional warlords, but has little authority outside the capital.
Afghanistan faces a long struggle to rebuild
The BBC's Sanjoy Majumder in Kabul says there is an urgent need to control the violence ahead of planned national elections next year.
The UN delegation says it will investigate how the expanded Nato mandate could best be used to extend the central government's influence.
But troop contributors remain reluctant. A top Nato commander who is visiting Kabul says that so far only Germany has offered soldiers for new missions outside the capital.
And the BBC's regional analyst Pam O'Toole says many aid agencies, and ordinary Afghans, believe the international community has failed to provide two essential ingredients - security and sufficient cash.
Drugs production is booming, and the UN has warned there is a risk that Afghanistan could again turn into a failed state, this time in the hands of drug cartels and narco-terrorists.
"No go" areas for aid workers are increasing. Ten aid workers have been killed since March and half of Afghanistan's 32 provinces have zones deemed high risk for aid organisations.