Libyan rebels say they have seized the government's last functioning oil refinery in a city west of Tripoli, as they continue to push towards the capital in a bid to force leader Muammar Gaddafi from power. The rebels on Thursday said they were in control of the refinery in Zawiya, 50 kilometers west of the capital. According to residents fleeing Zawiya, the opposition forces control most of the city. Clashes also continued on the eastern front in the strategic city Brega, where rebels said 18 of their fighters were killed and at least 33 wounded on Tuesday. Opposition forces are attempting to dislodge pro-Gaddafi troops from the oil port and refinery, which has not operated for months. Meanwhile, the U.S. military has deployed two more armed Predator drones for surveillance operations over Libya, where opposition fighters remain heavily dependent on NATO air power.