MISRATA, Libya - Government tanks launched an assault Friday on Misrata, rebels said, as NATO reported its warships had stopped Moammar Gaddafi's forces from laying mines in the besieged city's harbor.
Fierce fighting which had raged for days for control of Libya's Dehiba border crossing into Tunisia, meanwhile, hit a lull on Friday, but armed rebels were on guard in expectation of a new offensive, witnesses said.
"Four tanks attacked the city and one has been destroyed so far," said Ibrahim Ahmed Boushagha, a rebel fighter who accompanied a wounded man back from the front in Misrata.
"They took up positions during the night on the airport road, and tried to enter the city. We've stopped them at the outer limits, at least for now."
He said his group had come under mortar and rocket-propelled grenade fire, and three or four of them were wounded.
AFP journalists reported whistling sounds followed by a volley of detonations from the direction of the airport early afternoon, with an enormous plume of grey smoke rising over the area.
A constant stream of casualties was brought in to the city's main hospital, with several rebels saying the men had been wounded in a counter-attack by regime forces.
Earlier, fierce clashes and continuous explosions were heard in the suburbs, an AFP journalist said, and at midday the hospital reported a toll of two dead and 16 wounded.
Dr Khalid Abu Falra of the city's medical committee said a small clinic in the western suburbs also reported at least three deaths.
"All of our operating theatres are full," he said. "NATO must quickly intervene, as in previous days."
The airport battle, just southwest of the city limits, followed overnight barrages of rocket and mortar fire by Gaddafi's forces on the city, about 215 kilometers (130 miles), east of Tripoli.
Western Misrata also came under seemingly indiscriminate mortar and rocket fire on Friday as a NATO warplane flew overhead, witnesses and medics said.
Gaddafi's forces were pushed back from Misrata by the rebels and a series of NATO air strikes on Monday but had remained within rocket range of the city.
The rebels said earlier in the week they had secured the port and that their next objective was to seize control of the airport from government troops.
"Attack is the best form of defence," said Ibrahim Bet-Almal, who heads the rebel military forces in the area.
"Gaddafi is sending reinforcements to the region every day," he added.
British Brigadier Rob Weighill, director of NATO operations in Libya, said NATO warships stopped pro-Gaddafi forces on Friday from laying water mines in Misrata's harbor.
"Our ships intercepted the small boats that were laying them and we are disposing the mines that we found," Weighill told reporters via videoconference from his headquarters in Naples, Italy.
"It again shows his complete disregard for international law and his willingness to attack humanitarian delivery efforts," he said.
In western Libya, the alliance said meanwhile that its warplanes would focus on Gaddafi forces threatening the towns of Zintan and Yefren, scenes of heavy fighting between regime and rebel forces.
"We can see that there's a lot of offensive operations being conducted by pro-Gaddafi forces in the areas of Zintan and Yefren and clearly that's going to be a focus for us," NATO's Libya operations chief, Brigadier Rober Weighill, said in Brussels.
The situation at the Dehiba border post was calm following a day of heavy fighting, an AFP reporter and witnesses said, adding government troops appeared to have retreated into Tunisia.
They said the post was firmly in the hands of the rebels, who retook it Thursday evening in clashes that killed eight loyalist soldiers, only hours after Gaddafi forces had overrun it.
On the Libyan side of the border, the rival camps exchanged artillery fire in the early evening Thursday, causing panic among civilians, a witness told AFP.
Several ambulances from Tunisia crossed into Libya to evacuate the wounded, witnesses said.
A Tunisian police source said 5,150 people had crossed from Libya into Tunisia at Dehiba within 48 hours as the fighting raged.
In Brussels, rebel military chief Abdulfatah Yunis, formerly Gaddafi's interior minister, urged the West to deliver heavy weapons and warned that the strongman could use mustard gas on them in a bid to stay in power.
"Gaddafi is desperate now. Unfortunately he still has about 25 percent of his chemical weapons, which maybe he will use since he's in a desperate situation," Yunis told a news conference.
In Paris, the military said French jets were dropping inert bombs packed with concrete instead of explosives to destroy Gaddafi tanks without killing civilians.
Spokesman Thierry Burkhard denied rumors that the use of the 300-kilogram (660-pound) training devices was prompted by a shortage of real bombs, adding that the first such strike crushed an armored vehicle on Tuesday.