World stocks swung between gains and losses Monday, as hopes the Federal Reserve might take action to keep the U.S. from slipping back into recession offset fears of a global slowdown.

Brent crude fell to near $106 a barrel as Libyan rebels captured most of Tripoli, boosting hopes the OPEC nation's oil exports could resume soon. The dollar was stronger against the yen but weaker against the euro.

U.S. President Barack Obama said as momentous scenes unfolded in Tripoli Sunday that Moammar Gadhafi's regime had reached a "tipping point" and the Libyan "tyrant" must leave now to avoid further bloodshed.

In a written statement, Obama also looked to the post-Gadhafi era, calling on Libyan rebels who have surged into Tripoli to respect human rights.

Libyan rebels surged into Tripoli Sunday in a final drive to oust Moammar Gadhafi, seizing swathes of the capital including the symbolic Green Square and arresting the strongman's son, Seif al-Islam.

U.S. President Barack Obama said the Gadhafi regime was at a "tipping point" and that the "tyrant" must go, adding a call for the rebels to respect human rights and move to democracy.

Libya's former Prime Minister Abdessalam Jalloud is in Italy, Defense Minister Ignazio La Russa told reporters on Sunday, confirming reports that he had flown to Italy after defecting.

"Gadhafi's former number two is indeed in Italy," La Russa said, referring to Jalloud -- a popular figure who was once a close ally of Moammar Gadhafi but had been distanced from politics in recent years.

The Libyan conflict appears to be drawing to a close, Italian Foreign Minister Franco Frattini said in an interview on Sunday in which he also looked forward to economic deals for Italy under a new regime.

"Everything points to this tragedy coming to an end," Frattini told the Il Mattino daily, as NATO-backed rebels and Libyan leader Moammar Gadhafi's supporters fought skirmishes in the streets of the Libyan capital Tripoli.

A beleaguered Moammar Gadhafi urged supporters Sunday to "march by the millions" and quash a months-long uprising, as strong explosions rocked Tripoli amid fighting between rebels and regime supporters.

The blasts were heard shortly after 4:00 am (0200 GMT) in the heart of the city as NATO warplanes flew overhead, an AFP journalist said. The targets were not immediately identifiable but witnesses reported clashes in several quarters between insurgents and Gadhafi supporters.

Libyan rebel chief Mustafa Abdel Jalil said on Saturday "the end is very near" for Moammar Gadhafi and that it will be "catastrophic," as insurgents pushing on the capital claimed to have seized a third key town in 24 hours.

"We have contacts with people from the inner circle of Gadhafi," said the chairman of the rebel National Transitional Council (NTC). "All evidence (shows) that the end is very near, with God's grace."

Libyan rebels have taken "all" of the strategic oil hub of Brega in the east of the country, a rebel military official told Agence France Presse on Saturday.

"The industrial zone is under our control, all Brega is now under our control," the top-ranking official said on condition of anonymity, a day after rebels claimed they had seized two other key towns as they pushed their advance on the capital Tripoli.

Libyan rebels said they seized control of Zliten from Moammar Gadhafi's forces on Friday, only hours after reporting they were in the center of the town, 150 kilometers east of Tripoli.

"Zliten is now under the control of our fighters, but the fighting is not finished," the Information Center For Misrata Military Council said.

Strong explosions rocked Tripoli early Friday as Moammar Gadhafi's shaky regime called for a immediate ceasefire in Libya and rebels claimed control of a key oil refinery not far from the capital.

A slew of explosions were heard around 1:00 am (23:00 GMT) in the heart of the seaside capital where Gadhafi's residential complex is located, as well as in several areas in the west of the city.