The U.S. sixth fleet has attacked Libyan ships near the port city of Misrata, where pro-Gaddafi forces had made significant advances, according to the latest reports from the Libyan war theater.

BBC has reported that Gaddafi's war ships have been indiscriminately firing at merchant ships near Misrata.

A US Navy P-3C Maritime Patrol aircraft, a US Air Force A-10 Thunderbolt attack aircraft and guided-missile destroyer USS Barry engaged Libyan Coast Guard vessel Vittoria and two smaller crafts, a statement from the US Africa Command said. The Command said the attack took place late Monday.

Earlier, AFP reported that pro-Gaddafi forces swept through Misrata, dealing a heavy blow to the rebel forces. Control of Misrata is strategically important as it is the lone rebel stronghold in the west of the country. Gaddafi forces had eased off attack on Misrata over the weekend as western forces unleashed air fire to cover for the rebel positions.

Gaddafi would set much store by Misrata as keeping the port city will allow him to control the entire western flank as a contiguous unit. The city is 210 kilometers from Tripoli.

Meanwhile, the U.S. ambassador to the United Nations Susan Rice said Washington has not ruled out arming the rebels in Libya.She also says the US is looking for actions by those who surround Col Gaddafi. She adds there is no evidence Col Gaddafi is prepared to leave power, BBC reported.