NEW YORK - March 8 - The Libyan government and opposition forces should immediately grant aid agencies safe passage to violence-stricken areas of western Libya and allow civilians to flee the fighting, Human Rights Watch said today.

United Nations relief agencies, the International Committee of the Red Cross (ICRC), and nongovernmental organizations have said they cannot access western Libya because of security concerns.

"Both the Libyan government and opposition forces need to allow unhindered access for aid organizations to assist civilians," said Bill Frelick, refugee program director at Human Rights Watch. "People living in areas of heavy fighting in western Libya are now in dire need of medical aid and other assistance."

The number of people crossing Libya's western border into Tunisia has dropped sharply after pro-government forces assumed control of the border area on March 3, 2011, raising concerns that civilians might face restrictions on leaving areas of heavy fighting, Human Rights Watch said.

"We are deeply concerned that pro-government forces may be denying people their right to flee the fighting and leave the country," said Frelick.

Several days of intense fighting between government and opposition forces in the western cities of Zawiya and Misrata have put civilians at grave risk, Human Rights Watch said. Casualty figures reported by the media range from dozens to more than 100 dead in these cities, but it has not been possible to verify the full impact of the fighting on the civilian populations. Phone lines to both cities appear to be down.

"Civilians in Zawiya and Misrata are at grave risk," said Frelick. "Both sides should allow people to leave the area, and let desperately needed medical supplies in."

In parts of eastern Libya under control of anti-government forces, humanitarian organizations have been operating freely, Human Rights Watch said. Medical teams from the ICRC, for example, are working in coordination with the Libyan Red Crescent and the Benghazi Health Committee.

An important challenge in eastern Libya is the logistics involved in aid delivery and safely transporting the many migrant workers, especially sub-Saharan Africans, who wish to leave the country, Human Rights Watch said.