MISRATA, Libya - The port of a rebel-held city in western Libya was quiet Wednesday after NATO airstrikes drove back a determined government assault on the besieged city's lifeline.

The relative calm allowed an Albanian ship, the Red Star 1, chartered by the International Organization of Migration, to dock at the port of Misrata with 10 shipping containers of aid and two ambulances.

The ship was also there to evacuate refugees from the battered city that has become the main battlefield in the war between Moammar Gadhafi's forces and rebels seeking his ouster.

In Brussels, NATO confirmed that its warplanes had broken up an attack by pro-Gadhafi forces in Misrata on Tuesday night.

"NATO forces moved quickly to break up a force advancing on Misrata port," spokeswoman Carmen Romero said. "Several NATO aircraft were directed to the area, and following careful assessment of the risk to civilians, our pilots struck."

Damage assessments showed that six military vehicles and seven "technicals" -- civilian trucks equipped with machine guns or rocket launchers -- were hit. One surface-to-air missile site near Misrata was also destroyed, she said.

On Wednesday, the Misrata port bore signs of shelling, including a pillar of black smoke from a burning heap of tires ignited by the bombardment.

Next to the tires sat the blackened shells of some 250 brand new cars, all burnt to a crisp, surrounded by pools of melted metal and glass from the fire.

Misrata's port has served as a lifeline for the city, allowing in desperately needed medical supplies and food and ferrying out residents looking to flee the fighting that has left swaths of the city in ruins.

The battle for Misrata, which has claimed hundreds of lives in the past two months, has become the focal point of the armed rebellion against Gadhafi in the western half of the country since fighting on the eastern front near the city of Ajdabiya has become deadlocked.

The Libyan government has denied that it engages in indiscriminate shelling of civilian population centers.

The United Nations Security Council used evidence of attacks on civilians as grounds for its resolution authorizing an international campaign of airstrikes against Gadhafi's forces which has neutralized much of their heavy weapons and staved off total rebel defeat in the east.

British Defense Minister Liam Fox said Tuesday that the airstrikes have helped put the regime on its "back foot" and aided the rebels in making progress, though for the past weeks, there has been little movement on any of the war's fronts.

"There is little doubt across the alliance that this key contribution has proven to be of immense value protecting civilians in Misrata and have helped opposition forces to defend themselves against this brutal regime there," he said.