Analysts say moving forces into the city provided the Libyan leader's military with cover and increased the risk of civilian casualties

A formidable array of firepower had been positioned around Libya ahead of fresh efforts to subjugate Muammar Gaddafi. In terms of airpower alone, hundreds of state-of-the-art jet fighters are currently at locations from where they can easily strike the north African state. They include F-16s, used on missions in Afghanistan and Iraq, along with the G4 Tornado ground attack aircraft that forged its reputation in attacks using smart bombs against Iraqi military sites and runways during the Gulf war.

Most of the fighters are stationed in southern Italy, including the strategic US base at Gaeta, with Sicily less than 600 miles from Benghazi.

Six Danish F-16s landed at the base in Sigonella, Sicily, on Saturday and will be ready for operations on Sunday.

The first wave of fighters involved in the opening strikes against pro-Gaddafi forces took off yesterday afternoon from the military base of Saint Dizier, eastern France. Around 20 Rafale aircraft, armed with laser-guided air-to-ground missiles, precision-guided bombs and 30mm cannon were involved in the initial sortie.

France alone has around 100 warplanes, mainly Rafale and Mirage 2000 jets. Its aircraft carrier Charles de Gaulle will head toward the Libyan coast. Six Canadian CF-18 fighter jets have arrived in Italy and will be ready to enforce the no-fly zone on Sunday.

On Saturday night, shortly after nightfall, David Cameron announced British fighters were in action above Libya. The prime minister said the action was "necessary, legal and right". Almost simultaneously the Pentagon confirmed that the US had opened fire with Tomahawk missiles on Libya's air defence system around Tripoli.

Analysts believe the sudden storming of Benghazi by pro-Gaddafi forces was a military ploy designed to negate the potency of international air strikes. Moving his ground forces from the flat, exposed terrain of the desert to the west of Libya's second city and into its streets not only provided Gaddafi's troops with vital cover, but increased the risk that coalition air strikes would inflict civilian casualties.

As British military jets prepared to strike, experts warned that the consequences of collateral damage would create a propaganda coup for the Libyan leader, while potentially damaging the conviction of the coalition.

Hundreds of cars packed with people were reported to be fleeing the city in the hours before confirmation arrived that French Rafale fighter jets had flown into Libyan airspace.

The announcement of an initial strike by French airpower on a Libyan military vehicle directly followed a Paris meeting of world leaders to ratify the chronology of military intervention. Those present included Cameron, the US secretary of state, Hillary Clinton, and Arab and other European leaders.

However, sources at the Ministry of Defence refused to comment on British planes attacking pro-Gaddafi positions amid speculation Typhoon and Tornado fighters had arrived on Saturday at air bases in Cyprus or Italy.

Analysts said Gaddafi's "devious move" to announce and then break a ceasefire declared on Friday had been compounded by the decision to invade Benghazi. Shashank Joshi, an associate fellow of the Royal United Services Institute, an independent thinktank, said the tactic of entering the city of 670,000 had potentially "blunted" the airpower stacked against Gaddafi's forces.

While British Tornado and Typhoon fighters could easily eradicate troops and tanks assembled on the desert outside Benghazi, the mission becomes vastly more complex now that his forces have entered the city.

Joshi said: "It makes airpower considerably less effective. Given that some of Gaddafi's most pernicious weapons – ground-based artillery and tanks – are now intermingled with the urban infrastructure and civilian targets like schools and hospitals, it does blunt one of the international coalition's greatest strengths, which is advanced fast jets with precision targeted weaponry."

Another concern is avoiding hitting British special forces units, which are likely to be operating in the city to help "light up" targets and offer ground-level intelligence.

Paul Smyth, a former wing commander with the RAF, Tornado navigator and founder of defence analyst R3I Consulting, said it was technically possible to hit targets in built-up areas from a Tornado, although there were obvious challenges hitting a tank behind a building while moving at 600mph.

However, he said the continued expansion eastwards of pro-Gaddafi troops had presented international forces with a golden opportunity to deliver a crushing blow against the Libyan leader.

"Gaddafi's forces have travelled a long distance and require long lines of supply and communication. Whether they have the means required to sustain combat is open to question," he said.

Smyth added that even if Gaddafi's troops had made substantial progress in recapturing Benghazi, the rebels' determination to hold their positions would have been boosted by the arrival of international forces.

Knocking out Gaddafi's command structure or jamming his military communication networks is likely to happen quickly, although Libya's air defence system is itself considered antiquated, comparable to the Soviet systems that international forces faced during the Gulf war of 1991 and the Balkans campaign. In fact, much of Gaddafi's weapons stock is Soviet era with his air force – thought to involve up to 80 operational aircraft – relying on the MiG-23, which was phased out of Russian service 17 years ago. Ground forces rely on Soviet-era weaponry including T-72 tanks that entered production 40 years ago.

Among the munitions Britain is likely to deploy against ground forces is the Brimstone "fire and forget" anti-tank missile with a range of up to 12 miles and the sophisticated Storm Shadow, an air-launched cruise missile that can eradicate static targets from up to 155 miles.

It remains a possibility that airborne firepower will be supplemented with unmanned aerial surveillance drones like the advanced US Predator that can loiter above a battlefield and ensure there is no risk of civilians being killed before attacking positions with Hellfire missiles.

How long the airborne attacks will continue is anybody's guess with leaders of the country's involved hoping to avoid being embroiled in a long-running and resource intensive campaign. Joshi said: "How long can we correlate the status quo? Can we keep Typhoons in southern Europe for the next 10 years? Can we keep a no-fly zone in place, like over Iraq, for 12 years? The political decisions are not in place for that."