Muammar Gaddafi's armed forces are continuing to attack Libyan towns and cities despite three nights of western air strikes and another day of missile strikes.

Gaddafi's troops shelled rebels regrouping in the desert dunes outside the strategic eastern town of Ajdabiya, as well as civilians in the rebel-held western city of Misurata.

The onslaught came amid further wrangling over who should spearhead the western air campaign and the news that a US fighter jet had crashed in Libya, apparently because of mechanical failure.

The wreckage of the F-15E Strike Eagle jet was found near Benghazi, and both airmen were safely retrieved after ejecting before the crash.

Coalition leaders have confirmed Gaddafi's command-and-control sites have again been targeted with missile attacks and discussions are continuing as to who will have future control of the intervention.

People in Misurata said four children had been killed when the car they were travelling in was hit, bringing the death toll in the city to at least 44 in the last two days.

Residents painted a grim picture of the situation in the city, which Gaddafi loyalists have besieged for weeks, saying doctors were operating on people with bullet and shrapnel wounds in hospital corridors, and tanks were in the city centre.

"The situation here is very bad. Tanks started shelling the town this morning," a resident called Muhammad told Reuters by telephone from outside the city's hospital, adding: "Snipers are taking part in the operation, too. A civilian car was destroyed, killing four children on board. The oldest is aged 13 years."

Al-Jazeera reported that Gaddafi's forces were trying to seize the western rebel-held town of Zintan, near the Tunisian border, in an attack using heavy weapons. Residents had already fled the town centre to seek shelter in mountain caves.

Rebels in eastern Libya were positioned just outside Ajdabiya, making no further advance on the town despite the continuing air strikes.

At the frontline, in desert scrub about three miles outside the town, which marks the gateway to the rebel-held east, rebels said air strikes were helping cripple Gaddafi's heavy armour. But there was no sign of a swift drive forward.

When asked why rebel units had not advanced towards their objective – which is, eventually, Tripoli – Ahmed al-Aroufi, a rebel fighter at the frontline, told Reuters: "Gaddafi has tanks and trucks with missiles."

The crash of a F-15E fighter jet over Libya on Monday night was the first lose of a coalition plane since intervention began.

A Marine Corps Osprey search-and-rescue aircraft picked up the pilot, while the second crew member, a weapons officer, was recovered by rebel forces and is now in US hands.

Vince Crawley, a spokesman for the Africa Command, said the crash was likely to have been caused by mechanical failure rather than hostile fire.

It has also emerged that US and British submarines have launched 24 Tomahawk cruise missiles at Libyan command-and-control sites in the last 24 hours, bringing to 160 the total number of Tomahawk strikes.

With anti-Gaddafi rebels struggling to create a command structure that can capitalise on the air strikes, western nations have still to decide who will take over command once Washington pulls back.

The US will cede control within days, President Obama said, even as divisions in Europe fuelled speculation that Washington would be forced to retain leadership of air patrols that will replace the initial bombardment.

"We anticipate this transition to take place in a matter of days and not in a matter of weeks," Obama told a news conference while on a visit to Chile.

The British prime minister, David Cameron, said the intention was to transfer command to Nato, but France said Arab countries did not want the US-led alliance in charge of the operation.

Nato officials resumed talks in Brussels after failing to reach agreement at heated talks yesterday.

Underlining the differences in the anti-Gaddafi coalition, Italy's foreign minister, Franco Frattini, said if agreement were not reached on a Nato command, Italy would resume control of the seven airbases it has made available to allied air forces.

A Nato role would require political support from all the 28 states. The Turkish prime minister, Tayyip Erdogan, whose country is a Nato member, said today the UN should be the umbrella for a solely humanitarian operation in Libya.

In a speech in parliament, Erdogan said: "Turkey will never, ever be a side pointing weapons at the Libyan people."

Rifts are also growing in the world community over the UN resolution, with the Russian prime minister, Vladimir Putin, comparing the mandate to a call for "medieval crusades".

China and Brazil have also urged a ceasefire amid fears of civilian casualties, while the Algerian foreign minister, Mourad Medelci, described the western military intervention as "disproportionate" and called for "an immediate cessation of hostilities and foreign intervention".