* Interim leader tells Gaddafi forces to surrender by Saturday
* Gaddafi wife, three children in Algeria, daughter gives birth
* Anti-Gaddafi commander says war has killed some 50,000
* Tripoli still lacks water, power on eve of Muslim feast
* Gaddafi son's bodyguard says leader left Tripoli on Friday (Recast, adds details of family flight, oil chief)
By Samia Nakhoul and Alexander Dziadosz
TRIPOLI/BENGHAZI, Aug 30 (Reuters) - Forces loyal to deposed ruler Muammar Gaddafi held out in a few Libyan towns on Tuesday even though their leader has gone to ground and most of his family has fled the country.
As anti-Gaddafi fighters converged on his birthplace Sirte from east and west, Libya's interim council gave the loyalists holed up there a four-day deadline to surrender or face a bloody end.
"By Saturday, if there are no peaceful indications for implementing (a negotiated surrender), we will decide this matter militarily. We do not wish to do so but we cannot wait longer," council chairman Mustafa Abdel Jalil said.
Gaddafi's wife Safia, and his sons Hannibal and Mohammed entered Algeria on Monday morning, along with their children, Algeria's Foreign Ministry said.
His pregnant daughter Aisha was also among the party and she gave birth within a day to a girl, a source close to Algeria's health ministry said.
The interim council accused Algeria of an act of aggression in giving refuge to the family. But Algerian officials said the plight of the expectant mother weighed on the decision.
The baby was born in Djanet, according to two Algerian official sources. An oasis deep in the Sahara, Djanet lies about 60 km (40 miles) from the Libyan frontier and 500 km southwest of Sabha, one of the last bastions of support for Gaddafi.
Aisha, who is in her mid-30s, was on the very point of giving birth when the family appealed to cross the border, an Algerian source said.
Muammar Gaddafi's whereabouts have not been generally known since his foes seized his Tripoli compound on Aug. 23, ending his 42-year rule after a six-month revolt backed by NATO and some Arab states.
Britain's Sky News, citing a young bodyguard of his son Khamis, said the fallen leader had stayed in Tripoli until Friday when he left for Sabha.
It quoted the captured 17-year-old as saying Gaddafi met his son Khamis, a feared military commander, at around 1:30 p.m. on Friday in a Tripoli compound that was under heavy rebel fire. Gaddafi had arrived by car and was soon joined by Aisha.
After a short meeting, they boarded four-wheel drive vehicles and left, the bodyguard told a Sky reporter, adding that his officer had told him: "They're going to Sabha."
Some anti-Gaddafi officers have reported that Khamis Gaddafi and former intelligence chief Abdullah al-Senussi were both killed in a clash on Saturday. This has not been confirmed and NATO said it had no word on Khamis's fate.
At forward positions of NTC forces, on the main coastal road some 100 km (60 miles) west of Sirte, a Reuters correspondent saw little sign of military action on Tuesday.
The NATO spokesman said the alliance, which has kept up a five-month bombing campaign, was targeting Sirte's approaches
More NTC forces were heading for Bani Walid, a Gaddafi tribal stronghold 150 km (95 miles) southeast of Tripoli.
"Our fighters are now 30 km from Bani Walid," said Mohammed Jamal, a fighter at a checkpoint on the road to the town. "Hopefully Bani Walid will also be liberated soon. Right now there are still many Gaddafi supporters there."
Six months of fighting has left some 50,000 dead, one anti-Gaddafi commander said, an estimate that was hard to verify and which included many people who had gone missing.
"In Misrata and Zlitan between 15,000 and 17,000 were killed and Jebel Nafusa took a lot of casualties. We liberated about 28,000 prisoners. We presume that all those missing are dead," said Colonel Hisham Buhagiar.
"Then there was Ajdabiyah, Brega. Many people were killed there too."
An NTC spokesman said it would seek to extradite Gaddafi's relatives from Algeria, which is alone among Libya's neighbours in not recognising the de facto government and previously opposed sanctions and a no-fly zone against Gaddafi.
Nearly 60 countries have acknowledged the NTC as Libya's legitimate authority. Russia, China, India, South Africa and Brazil are among those which have so far withheld recognition.
Abdel Jalil, the council chairman, who was previously Gaddafi's justice minister, called on Algeria to hand over any of the former leader's sons on its wanted list.
A visit to a Tripoli beach compound used by Gaddafi's children and members of his elite revealed a life of opulence and privilege that many Libyans could barely dream of.
Saadi Gaddafi's chalet was strewn with designer clothes, including some unworn suits, and about 100 pairs of shoes. Aisha's house boasted 13 bedrooms and gold-plated cutlery.
Anti-Gaddafi fighters now sleep in the bedrooms of their former rulers, whose gated compound has tennis courts, football pitches and dining centres, along with magnificent sea views.
Many Libyans were overjoyed at the fall of Gaddafi, which followed that of longtime rulers in Egypt and Tunisia earlier this year, but have been chilled by evidence of mass killings in Tripoli as his forces fought losing battles with rebels.
But a week after Gaddafi's fall, Tripoli's two million people remain without running water or electricity. Banks, pharmacies and many other shops are still closed. The stench of garbage and sewage still pervades despite clean-up efforts.
A council spokesman said a pumping station for Tripoli's water supply that lies in a pro-Gaddafi area had been damaged and could not be reached for repair.
The European Union's humanitarian office said pro-Gaddafi forces in Sirte had cut two-thirds of the water supply to Tripoli, most of which comes from the "Great Man-made River", a huge project built under Gaddafi that pumps out water from under the Sahara desert.
Aid agency Medecins sans Frontieres (Doctors without Borders) said hundreds of African migrants and refugees in desperate need of medical attention were hiding in makeshift camps in Tripoli.
"Many of these people already fled from fighting in their home countries, such as Somalia, Sudan or other African countries," said Simon Burroughs, MSF's emergency coordinator in Tripoli. "Some people came to these makeshift camps looking for a way to cross by boat to Europe. All of them remain trapped with nowhere to go."
One community of around 1,000 refugees and migrants lives in and around boats on an abandoned military base, MSF said.
In Benghazi, headquarters of the rebel movement during the war, the newly-appointed chairman of the National Oil Corporation said oil production can restart within weeks and will reach full pre-war output within 15 months.
"Starting up production will be within weeks, not months," Nouri Berouin, chairman of the NOC, told Reuters.
The OPEC member was producing 1.6 million barrels per day before the uprising began, causing foreign workers to flee.
"I have met with international oil companies and the first thing I told them was that we respect all contracts," he said. (Additional reporting by Mohammed Abbas in Tripoli, Maria Golovnina in Misrata and Emma Farge and Robert Birsel in Benghazi; Writing by Alistair Lyon and Alastair Macdonald; Editing by Angus MacSwan)