Fears are growing for civilians caught up in fighting between government forces and the Taliban in Afghanistan's southern Helmand province.
There have been several days of clashes as Afghan forces, supported by US air strikes, try to defend Helmand's strategically important capital, Lashkar Gah, from a Taliban assault.
It is estimated that about 35,000 people have so far fled their homes.
Amnesty International called on both sides to give civilians "safe passage".
The group said the fighting had taken out power in Lashkar Gah and shut down telecommunication networks, and that all exit routes from the city had been blocked.
"The situation for civilians in Lashkar Gah is grave and could deteriorate rapidly in the coming days. Tens of thousands of people are trapped in the middle of a bloody battle that shows no sign of abating," Omar Waraich, head of South Asia at Amnesty International, said in a statement.
The United Nations Assistance Mission in Afghanistan earlier called on both sides to "take all feasible measures to protect civilians", including "safe paths for those wishing to leave".
Aid agencies are reporting that many civilians are now sleeping on the streets without shelter.
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