Gunfire heard in Tripoli.

TRIPOLI, Libya – Gunfire has broken out in the Libyan capital of Tripoli.

Frequent bursts of gunfire could be heard around Tripoli early Sunday, one day after government forces in tanks rolled into the opposition-held city closest to the capital. Also Saturday, rebels captured a key oil port and pushed toward Moammar Gadhafi's hometown in a seesaw for both sides in the bloody battle for control of Libya.

The rival successes signaled an increasingly long and violent battle that could last weeks or months and veered the country ever closer to civil war.

It was not immediately clear who was firing on Sunday.