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Inside the besieged city of Misrata, spent rockets protrude from the pavement of a parking lot, unarmed teenagers prepare plastic crates of Molotov cocktails, and fighters at roadblocks sit inside empty shipping containers outfitted with furniture, carpets and generator-powered TVs and watch Al-Jazeera reports of their war with Muammar al-Qaddafi.

For nearly two months, Qaddafi's forces have laid siege to the only major city in western Libya still in opposition hands, and its residents said the attacks have been relentless and hundreds of people have been killed. A British war photographer who was an Oscar-nominated co-director of the documentary "Restrepo" and a New York-based photographer for Getty Images were killed while covering the fighting in the city Wednesday.

"The number of artillery shells and mortars is truly amazing," said Abdul-Athim Salim, a geography professor at the local university. "The only break is when they are changing ammunition. Other than that, it's continuous. It just keeps going. Boom, boom, boom!"

Qaddafi's forces have intensified their assault on Libya's third-largest city, firing tank shells and rockets into residential areas, according to witnesses and human rights groups. NATO commanders have admitted their airpower is limited in being able to protect civilians in a city — the core mission of the international air campaign.

France vowed Wednesday to step up airstrikes.

The government troops are deployed along Tripoli Street, a downtown thoroughfare, while well-organized groups of rebels man checkpoints every few hundred yards (meters) in opposition-controlled areas, flash the "V'' sign and shout, "Victorious! Victorious!"

Palm trees are everywhere, and defensive sand berms three or four feet tall line areas near the Mediterranean.

Most of the Qaddafi troops are centered to the south and west of the city of 300,000, and many of the residents who had lived in those areas fled to the northern part of the city by the sea. There were about four areas of intense fighting in the city on Wednesday, and everyone seemed to know where the battle lines are.

The port is quiet, with the only signs of violence being a hole in the roof of a warehouse or a blasted and blackened shipping container with charred contents. At the dock sat a Red Cross boat, a large tug and a ship flying a Turkish flag where a crane unloaded crates.

Random gunfire crackles during the day. Cinderblocks divide a road, with one lane for ambulances, one lane for everyone else.

Salim, 32, said the hardest part of living in the besieged city was security.

"About three times, I'd just been out driving my car and a mortar has landed in front of me on the road," he said.

Qaddafi's government has come under sharp international criticism for its assault on Misrata and been accused by human rights groups of using heavy weapons, including shells, missiles and cluster bombs. Such bombs can cause indiscriminate casualties and have been banned by many countries.

Libyan officials have persistently denied the army is shelling Misrata or using cluster bombs. "We welcome any objective investigation of the actions of our army, our government and our officials," said government spokesman Moussa Ibrahim. He said the international community should "not listen to media reports or stories fabricated by the rebels."

The U.N.'s top human rights official, Navi Pillay, said Libyan government forces may be committing war crimes by using heavy weapons against civilians in Misrata. She said Qaddafi's troops should be aware that their actions will be scrutinized by the International Criminal Court.

At Hilal Hospital in Misrata, Dr. Mohammed al-Fagieh said three bodies were brought in to the 45-bed facility on Wednesday, along with 12 people who were severely wounded and about 25 others with lesser injuries. That's about normal these days, he added.

Human rights activists have said more than 260 people have been killed in Misrata, with the final toll likely higher, and many more people wounded.

Two Western photographers were killed Wednesday in the city: Tim Hetherington, 40, a British-born war photographer and the Oscar-nominated co-director of the documentary "Restrepo," about U.S. soldiers on an outpost in Afghanistan; and Chris Hondros, 41, a New York-based photographer for Getty Images.

Two other photographers — Guy Martin, a Briton affiliated with the Panos photo agency, and Michael Christopher Brown — were treated for shrapnel wounds, doctors said.

Abdel Salam, a rebel fighter who wanted to be identified only by his given name for fear of reprisal, said earlier in the day that NATO planes flew overhead but did not carry out any airstrikes.

NATO Brig. Gen. Mark van Uhm said from the alliance's headquarters in Brussels said his forces have destroyed more than 40 tanks and several armored personnel carriers in Misrata, but there is concern of inadvertently harming civilians in such airstrikes.

"There is a limit to what can be achieved by airpower to stop fighting in a city," said van Uhm.

In addition to saying it was stepping up its airstrikes, France acknowledged Wednesday that it has military officers already working with Libyan rebels on the ground. Italy joined Britain in announcing their commitment of military instructors to train the rebels, who have failed to rout Qaddafi's forces despite weeks of NATO-led airstrikes.

But European powers and the Libyan opposition remained firm against sending in foreign ground troops.

The rebels now control most of eastern Libya, while Qaddafi's forces hold Tripoli and most of the west.

Besides Misrata, however, there are other rebel-held areas in western Libya, including the Nafusa mountain area that is home to Libya's Berber minority. The fighting in the mountain region has sent about 10,000 people fleeing into nearby Tunisia. Four mortar shells from the fighting landed on Tunisian territory Monday, Tunisian officials said.

If rebels in western Libya were to rise up across the region, it could break the deadlock that has marked the uprising.

Since the weekend, the town of Yifran, with a population of about 25,000, has come under daily attack with rockets, tank shells and anti-aircraft guns, said a rebel fighter, who would only give his first name, Belgassem, for fear of reprisals. Fighting also has been reported in the towns of Qalaa and Nalut.

Pillay, the U.N. human rights commissioner, urged Libyan authorities to halt their siege of the city and allow medical care to reach victims. Pillay says it is "clear that the numbers (of casualties) are now substantial, and that the dead include women and children."

Hundreds of migrant workers and wounded people have been evacuated by boats, which have also delivered humanitarian supplies, including food and medicine.

One of the major signs of distress were the gas lines, with about 30 cars waiting for fuel at a gas station.

A few shops were open, but most were closed. A shop selling generators appeared to be doing a big business, since it has been about two months with all electricity in the city cut off.

Generators were powering TVs that were set up inside empty shipping containers for the rebels watching the news. At one checkpoint, about 10 guards had pitched a tent and were smoking waterpipes while watching Al-Jazeera.