Human Rights Watch said on Monday indiscriminate attacks on civilians trapped in the Libyan city of Misrata by forces loyal to Muammar Gaddafi violate international law.
Hospitals in Libya's third city had documented about 250 deaths over the past month, most of them civilians, as government troops fight for control of the last big rebel stronghold in the west of Libya, the group said.
"We've heard disturbing accounts of shelling and shooting at a clinic and in populated areas, killing civilians where no battle was raging," Sarah Leah Whitson, Middle East and North Africa director at Human Rights Watch, said in a statement.
Under international law, warring factions are not allowed to target civilians or carry out assaults that do not discriminate between civilians and combatants, the New York-based organisation said.
The watchdog said it spoke to two doctors and 17 evacuees, including 35 year-old Jamal Muhammad Suaib, who lost three family members in an attack by government soldiers.
"My wife was holding my son," he was quoted as saying. "The bullet hit her in the arm and ricocheted into my son's face. None of us had a weapon. We were just families looking for (a) safe place to stay."
Libyan officials deny attacking civilians and say they are engaged in a battle against armed militia groups and al Qaeda sympathisers bent on destabilising the North African country.
Journalists have not been allowed to report freely from Misrata, making it difficult to verify the accounts.
Misrata is not the only place from where allegations that Gaddafi loyalists have waged a campaign of terror against civilians have emerged.
People fleeing the sparsely populated Western Mountains region say government troops are shelling homes, poisoning water wells and threatening to rape women. Gaddafi has long viewed the region's Berber people with suspicion.
In Misrata, children have also fallen prey to the conflict, the United Nation's children's agency UNICEF said, citing "at least 20 child deaths and many more injuries, due to shrapnel from mortars and tanks and bullet wounds".
Misrata rose up in revolt against Gaddafi's four-decade rule in mid-February along with other towns across the country. Gaddafi's forces have encircled the city and sought to loosen the rebels' grip with persistent shelling and sniper fire.
The humanitarian situation in the city of 300,000 people is an increasing worry, Human Rights Watch said. "The government has blocked all humanitarian aid via land routes," it said, adding this act, too, flouted international law.
Limited food and medical relief has arrived through Misrata's rebel-controlled port.