The alliance said the strike was carried out Saturday near the town of Tawurgha. It says the missile site was being used to launch indiscriminate attacks on Libyan civilians, including in Misrata.
Rebels struggling to push out from Misrata toward the capital Tripoli have faced stiff resistance from government forces loyal to leader Moammar Gadhafi.
The British military says it scuttled an effort by Gadhafi's naval forces Friday to conduct a raid near Misrata by firing on the troops' boats from a warship offshore.
Rebel forces have been trying to push out Gadhafi since an uprising erupted in February.