Nato is ill-equipped to probe accidental loss of life or prevent further civilian deaths during its latest offensive in Afghanistan, Amnesty International warned today.
The organisation claimed international forces lacked the "credible mechanism" needed to investigate recent incidents in which locals had been killed or ensure that such occurrences were not repeated.
It also hit out at "inexcusable" tactics employed by the Taliban, stating that knowingly endangering Afghan life could constitute a war crime.
It called on both sides in the conflict to comply with legal obligations to protect thousands of displaced Afghans and those still trapped in areas of intense fighting.
Nato responded to the comments by saying it was doing everything it could to limit civilian casualties and that any credible allegation would be fully investigated.
Amnesty International issued the warning following the deaths of at least 15 civilians so far during Operation Moshtarak.
Twelve were killed on Sunday when a house was struck by Nato rockets. A further three locals have since been killed in separate incidents.
Amnesty International's Asia-Pacific director Sam Zarifi said: "About 10,000 civilians have fled the conflict zone, but thousands more are caught up in the fighting."
Last year the war in Afghanistan saw around 2,400 civilians lose their lives as a result of the fighting, according to UN figures.
The Taliban were responsible for two-thirds of the deaths, while 25% of them were the result of actions by Nato or pro-government allies.
Heavier fighting this year could result in an even higher death toll, Amnesty warned.
Mr Zarifi said: "The US and Nato have made commitments to minimise civilian casualties.
"But international and Afghan forces still lack a consistent, clear and credible mechanism to investigate civilian casualties, provide accountability and ensure that such incidents do not recur.
"This is now particularly urgent with more than 30,000 extra foreign troops deployed in Afghanistan and apparently committed to a more aggressive military strategy."
Carmen Romero, deputy spokeswoman for Nato, said: "We are trying to do everything we can to limit civilian casualties and we are increasing our efforts.
She added: "Any credible allegation (of civilian death) is investigated by ISAF (International Security Assistance Force) in accordance with the Afghan government.
At the end of any investigation, Nato ensures that it is applying the right tactics to protect civilian life, Ms Romero said.
Amnesty International also attacked the Taliban for preventing civilians from leaving the conflict area, amid allegations that some were being used as human shields.
Mr Zarifi said: "The Taliban have a record of knowingly endangering Afghan civilians in their operations, which can constitute a war crime.
"Insurgent groups are bound by international law to take every possible precaution to protect the lives of civilians.
"The Taliban invoke international laws of war when it suits their purposes. Their failure to respect these laws is inexcusable and they should be held to account for their actions."