Attacks by Taliban fighters in Afghanistan have hit record highs this year with hundreds of civilians killed, including 19 aid workers.
The violence is spreading insecurity which has hampered relief work, aid groups say.
Unrest had spread to once stable areas and welfare agencies were forced to scale back aid delivery even as drought and food price hikes put millions of people in difficulty, the Agency Co-ordinating Body for Afghan Relief (Acbar) said on Friday.
"So far this year the number of insurgent attacks, bombings and other violent incidents is up by approximately 50 per cent on the same period last year," said Acbar, a grouping of about 100 Afghan and international non-governmental organisations.
Anja Debeer, co-ordinator of Acbar in Afghanistan, told Al Jazeera that the attacks had "greatly affected" the aid group's capability to operate and aid workers were being subjected to threats and kidnappings.
"Access to people in the greatest need of aid becomes more and more limited and so we will be less effective and efficient," she said.
"If you look at the drought situation and the increase in food prices where four million people are at risk, if it is not possible to get food to them in time, there could a famine."
Civilian death toll
There were 463 Taliban attacks in May and 569 in June, Acbar said in a statement, citing figures from a range of sources including the Afghanistan NGO Safety Office.
This was "greater than the number of such attacks in any other month since the end of major hostilities following the international intervention in 2001," it said.
"This year 2,500 people have reportedly lost their lives in the conflict and whilst exact figures are not yet available, this could include up to 1,000 civilians," the group said.
Initial estimates were that more than 260 civilians were killed in July, which has higher than any other month in the past six years, it said.
July saw some of the worst violence since the Taliban were ousted from government in a US-led invasion in late 2001.
A suicide bomb at the Indian embassy in Kabul killed around 60 people and other attacks left dozens more dead.
Nato troops killed
In the latest incidents, bomb blasts killed five Isaf soldiers on Friday, the multinational force said.
Isaf did not release the nationalities of its soldiers killed in eastern provinces along the border with Pakistan.
Four died with a civilian interpreter in the eastern province of Kunar, Isaf said in a statement that gave few details. Another died in a similar blast in Khost, it said.
Separately, five Afghan policemen were killed in an overnight bomb attack that was similar to scores carried out by the Taliban.
The men were killed late on Thursday in the southern province of Kandahar.
They were on patrol in Pajwayi when a remote-controlled bomb blew up their vehicle, deputy district police chief Bismillah Khan told the AFP news agency.
Two other officers were wounded, he said.