Citing the reported use of machine guns, snipers and military planes against demonstrators, Ms. Pillay said such extremely serious allegations of acts committed in brazen defiance of international law must not go without a full and independent investigation.

"Protection of civilians should always be the paramount consideration in maintaining order and the rule of law. The authorities should immediately cease such illegal acts of violence against demonstrators. Widespread and systematic attacks against the civilian population may amount to crimes against humanity," she stated.

A group of UN human rights experts also called on the Libyan Government to immediately cease the use of excessive and lethal force. "The situation in Libya is quickly spilling out of control with the Government targeting the very people it has been mandated to serve," they stated in a news release. "Adopting tactics such as the use of live ammunition to crush dissent is unacceptable."

The experts voiced concern about the reported use of military planes to attack protesters, the alleged involvement of foreign mercenaries in killing the protesters, and the arbitrary arrests of individuals including lawyers, human rights defenders and journalists.

The Director-General of the UN Educational, Scientific and Cultural Organization (UNESCO), Irina Bokova, voiced her alarm over the worsening situation in Libya and the continuing clampdown on media and vital information services.

"I call on the Libyan authorities to exercise maximum restraint. I also call on them to respect the right of people to access information, to be able to communicate with one another and for the media to be able to do its job," she stated.

"Attempting to silence people by repression, by denying them access to vital information services is a violation of basic human rights that can only fuel anger and frustration," she added.

Meanwhile, the UN High Commissioner for Refugees (UNHCR) said today that it has become increasingly concerned about dangers for civilians and especially for asylum-seekers and refugees in Libya as many may inadvertently be caught up in this violence.

"We have no access at this time to the refugee community. Over the past months we have been trying to regularize our presence in Libya, and this has constrained our work," Melissa Fleming, UNHCR's spokesperson in Geneva, told a news conference.

"Some of the reports we are getting from third-party sources are very worrying. A journalist has passed information to us from Somalis in Tripoli who say they are being hunted on suspicion of being mercenaries. He says they feel trapped and are frightened to go out, even though there is little or no food at home," she said.

Prior to the current unrest UNHCR had registered over 8,000 refugees in Libya, with a further 3,000 asylum-seekers having pending cases. The agency is asking all countries to recognize the humanitarian needs at this time of all people fleeing targeted violence, threats, and other human rights abuses in Libya.