A P-C3 Maritime Patrol aircraft fired at the Vittoria after multiple explosions were seen near the port Monday evening. The 12-metre patrol vessel had to be beached.
A U.S. Air Force A-10 Thunderbolt said it also fired on two smaller vessels, destroying one and forcing the other to be abandoned, said the statement from Joint Task Force Odyssey Dawn, which is providing operational and tactical command of U.S. military forces supporting the response to unrest in Libya.
"The purpose of firing onto the vessel was to stop them from firing into the port, harming civilians and damaging other vessels," Lt. Nathan Potter said.
Officials said they were in the process of assessing the damage caused by the Libyan vessel, including whether any civilians had been harmed, or if any vessels in the port had sustained damage.
It was one of the most direct confrontations between NATO personnel and forces loyal to Libyan leader Moammar Gadhafi since the former pledged airstrikes to protect civilians in the north African nation.
On Tuesday, Russia's envoy to NATO was urging coalition partners not to bomb Libyan ground targets as it works to enforce the UN resolution to implement an arms embargo and no-fly zone in and around Libya.
Russia, which abstained from voting on the Security Council resolution, says the international air campaign is overstepping its bounds.
Rebels trying to topple Gadhafi's 40-year reign on the country have used the cover of airstrikes to race along the coastline in recent days, retaking several oil towns.
But their charge westward has met resistance as they near the town of Sirte. Residents and forces loyal to Gadhafi fired at Libyan rebels on the road east of Gadhafi's hometown overnight, pushing them back towards the town of Bin Jawad, rebels said.
There are reportedly dozens of rebel fighters and civilians gathered with pickups and cars outside the town, which is about 150 kilometres from Sirte.