The Afghan government has launched a major offensive against Taliban forces near the north-eastern provincial capital of Kunduz.
The Taliban have come close to the city in recent fighting, leaving it cut off with tens of thousands of displaced.
A BBC correspondent who has flown into Kunduz has heard gunfire and artillery exchanges not far from its centre.
Afghan officials say foreign jihadists trained by the Islamic State group are fighting alongside the Taliban.
Provincial governor Mohammed Omer Safi said that the bodies of 18 foreign fighters including two women had been found.
Security forces and Taliban have been involved in a standoff for about a week after the insurgents launched an offensive on Kunduz at the end of April.
Correspondents say the advance is the most serious threat to a provincial capital in years.
Afghan army and police are involved in the fighting but there is no substantial help from foreign troops.
Only a few thousand Nato troops remain in the country, largely in training roles, after their combat mission ended in December.
People displaced by the fighting are spread across the city and rural areas of the province of Kunduz.
International aid agencies are trying to assist them, with the World Food Programme preparing emergency kits of flour, pulses, cooking oil and high-energy biscuits for 500 families, spokesman Wahiddullah Amini told Reuters news agency.
But the BBC’s David Loyn reported from Kunduz that if the fighting is prolonged it could lead to a bigger problem if there is a failure to bring in the harvest this month.
Source: BBC News
