Government forces in tanks rolled into the opposition-held city closest to Tripoli after blasting it with artillery and mortar fire, while rebels captured a key oil port and pushed toward Moammar Gadhafi's hometown in a seesaw Saturday for both sides in the bloody battle for control of Libya.

With the Gadhafi regime's tanks prowling the center of the city of Zawiya, west of Tripoli, residents ferried the wounded from the fierce fighting in private cars to a makeshift clinic in a mosque, fearing that any injured taken to the military-controlled hospital "will be killed for sure," one rebel said after nightfall.

The rival successes — by Gadhafi's forces in entering resistant Zawiya, and by the rebels in taking over the port of Ras Lanouf — signaled an increasingly long and violent battle that could last weeks or months and veered the country ever closer to civil war.

Rebels in the east advanced from their eastern stronghold toward Sirte, setting the stage for fierce fighting with pro-Gadhafi forces who hold sway in the tribal area.

Western leaders focused on humanitarian aid instead of military intervention, and the Italian naval vessel Libra left from Catania, Sicily, for the rebel-held port of Benghazi in eastern Libya, with 25 tons of emergency aid, including milk, rice, blankets, emergency generators, water purifying devices and tents. It is due to arrive early Monday.

The crisis in Libya has distinguished itself from the other uprisings sweeping the Arab world, with Gadhafi unleashing a violent crackdown against his political opponents, who themselves have taken up arms in their attempt to remove him from office after ruling the country for more than 41 years. Hundreds have been killed.