Yemeni President Ali Abdullah Saleh returned to Sanaa on Friday after more than three months of medical treatment in Saudi Arabia, even as his forces were battling dissident troops in the capital.

Saleh's surprise return was announced by state television. He arrived by plane in Sanaa at 5:00 am (02:00 GMT), an airport source told Agence France Presse.

Israel on Friday will raise its level of security alertness in case unrest accompanies Palestinian president Mahmud Abbas's application for U.N. membership for a Palestinian state, police said.

"We will be heightening security by one level in general. This is being coordinated by the military, border police and Israel police," police spokesman Mickey Rosenfeld told Agence France Presse.

Forces loyal to Libya's new rulers said they were holding back on Thursday from advancing on Moammar Gadhafi's last redoubts despite their capture of two key southern oases.

The commander of NATO's Libya air campaign, Lieutenant General Charles Bouchard, said he was confident the mission could be completed "well within" three months after the alliance extended it for another 90 days.

Al-Baghdadi al-Mahmoudi, Libya's former prime minister under Moammar Gadhafi, was arrested in Tunisia and jailed Thursday for six months for illegal entry, a Tunisian justice ministry spokesman told Agence France Presse.

Baghdadi, who was arrested on Wednesday, "appeared before the state prosecutor in Tozeur (430 kilometers south of Tunis) and sentenced to six months in prison with immediate effect," Kadhem Zine el Abidine said.

Deadly clashes spread across Yemen's capital on Thursday as tribesmen joined battles between rival military units, raising fears among frightened residents of a descent into civil war.

Soaring tensions between troops loyal to Yemeni President Ali Abdullah Saleh and his opponents torpedoed efforts on Wednesday by international mediators to promote a Gulf-initiated deal aimed at ending the political impasse that has gripped the country for months.

Around 1,000 Palestinians gathered in the West Bank city of Ramallah on Thursday to protest against U.S. President Barack Obama's speech to the United Nations.

The protesters carried signs deriding the United States and Obama for his address, in which he reiterated his opposition to the Palestinians' attempt to win U.N. membership for their state, saying there was no "shortcut" to peace.

NATO can achieve its mission in Libya within the next three months, the commander of the NATO military operation, Lieutenant General Charles Bouchard said Thursday.

Asked for an assessment a day after NATO allies extended their air campaign in Libya by another 90 days, Bouchard said at a press briefing in Brussels: "I'm highly confident we can complete this mission well within this timeframe."

Troops advancing on Moammar Gadhafi's hometown Sirte from the east have put off any offensive for a week for lack of ammunition, a brigade commander told Agence France Presse on Thursday.

"Fighting has been stopped for a week. We are facing a shortage of ammunition," said Commander Mustafa bin Dardef of the Zintan Brigade, whose troops are deployed on the front line 25 kilometers (15 miles) east of Sirte.

Palestinians on Thursday slammed U.S. President Barack Obama's address to the U.N. General Assembly, calling it a display of U.S. bias towards Israel.

Commentators, politicians and ordinary Palestinians alike said Obama's speech on Wednesday, just days before the Palestinians apply to become a U.N. member state, showed Washington was incapable of serving as a fair broker between Israel and the Palestinians.

Three security officials were killed in two separate attacks attributed to Kurdish rebels in east and southeast Turkey, local security sources said on Thursday.

Clashes with Kurdish rebels late Wednesday in a town in Van province in eastern Turkey resulted in the death of two Turkish security forces and left three others wounded, added the sources.