TRIPOLI, Libya - Forces loyal to Libyan leader Moammar Gadhafi shelled villages and towns to try to take control of the high ground in a western mountain range, while a UN official appealed for global assistance for some 2 million people displaced by fighting between Gadhafi's forces and rebels trying to oust him.

The United Nations humanitarian coordinator for Libya said some 1.6 million people inside the North African country need aid because fighting has disrupted basic services and depleted food and medical stocks.

Coordinator Panos Moumtzis, who is based in Geneva, an additional 500,000 who have crossed borders to Tunisia, Egypt and elsewhere in the region also need humanitarian assistance.

Moumtzis said he was asking international donors for $408 million to fund aid for Libya through September.

Gadhafi, who has ruled Libya for more than 40 years, has been using his military and militias to try to put down an uprising that began in February to try to remove him from power.

Also Wednesday, the International Criminal Court prosecutors warned Libyan officials they will be prosecuted if they attempt to cover up crimes by forces loyal to Gadhafi.

Prosecutors issued the warning in a letter to Libyan Foreign Minister Abdelati al-Obeidi.

The letter also formally informed him of Prosecutor Luis Moreno-Ocampo's request for arrest warrants for Gadhafi, his son Seif al-Islam Gadhafi, and intelligence chief Abdullah al-Sanoussi. The judges will now have to decide whether to issue arrest warrants.

Moreno-Ocampo on Monday accused the three Monday of murder and persecution for allegedly ordering, planning and participating in attacks on civilians.

The letter also underscored that the court has jurisdiction in Libya because its investigation was ordered by the UN Security Council -- a contention the Libyan government has rejected.

Libyan rebels said on Wednesday that Gadhafi's forces were shelling communities in the western mountains. BelJassem, a citizen-turned-fighter from a village near Yafrin, said Gadhafi forces were using Grad missiles and rocket launchers in their nearly monthlong siege, leaving residents trapped and cut off from food and medical supplies.

"We dig trenches and hide in there at night," says BelJassem, who gave only his first name for fear of reprisals.

Yafrin, which is 120 kilometres southwest of Tripoli, is one of the biggest cities in the Nafusa mountain range, home to the ethnic Berber minority.

Medghamas Abu-Zakhar, a rebel based in Yafrin, said Gadhafi forces were shelling villages toward the top of the Nafusa range in an attempt to capture the high ground.

Yafrin is home to some 250,000 Berbers, said Fathi Abu-Zakhar, who is among the city's residents who fled the fighting. He said that two of his sons stayed behind.

"They are living under siege," he said in a telephone interview. "No food and no medicine can get in. Even the injured have no way to get treatment since the only hospital has been shut down."

Farther to the West, Libyan shelling forced the closure late Tuesday of the so-called Wazen passage, which is the route people fleeing Libya use to get to neighboring Tunisia.

Jaber Naluti, a volunteer who has been trying to assist people in the area, said Gadhafi forces shelled the route, killing seven Libyan rebels. Some of the shells fell on the Tunisian side of the border.

Naluti said the shelling forced Tunisian authorities to close the passage. Tunisian jet fighters flew over the area but didn't fire. The passage appeared to be functioning normally on Wednesday.

The reports from Yafrin came a day after NATO said it would step up psychological warfare operations to try to persuade troops loyal to Gadhafi to abandon the fight.

Wing Cmdr. Mike Bracken, speaking in Naples, Italy, said NATO planes have been dropping leaflets and broadcasting messages to Libyan forces urging them "to return to their barracks and homes."

Bracken said the messages also have advised pro-regime troops "to move away from any military equipment" that could be targeted by NATO's strike aircraft.

He did not provide further details on the psychological operations. But the U.S. has been using a specially modified Air Force C-130 transport to broadcast messages to Libyan forces in AM, FM, high-frequency radio, TV and military communications bands.

NATO is operating under a U.N. Security Council mandate to maintain a no-fly zone and to take other actions to protect civilians from attack by Gadhafi's forces. In recent days, NATO attacks have concentrated on military and logistics hubs in Tripoli.

There was no formal reaction from the government to reports that Shukri Ghanem, the Libyan oil minister and head of the National Oil Co., defected earlier this week and left the country for Tunis. The defection was confirmed by Abdel Moneim al-Houni, a former Libyan Arab League representative who was among the first wave of Libyan diplomats to defect.

Others who have defected include Foreign Minister Moussa Koussa, one of Gadhafi's earliest supporters; Interior Minister Abdel-Fatah Younes; Justice Minister Mustafa Abdul-Jalil, and Ali Abdessalam Treki, a former UN General Assembly president. A number of ambassadors and other diplomats also have resigned.

The defections suggest Gadhafi's political structure is fraying, but it's unclear whether there is enough internal strife to seriously undermine his ability to fight rebel forces as NATO airstrikes pound Libyan military targets. Gadhafi appears to retain the backing of his core of military commanders.

Still, support for Gadhafi seems to be waning in the capital, Tripoli. Pro-regime demonstrations are sparsely attended, even when heavily advertised in advance.