Oil rose slightly on Wednesday, reversing earlier losses, as unrest flared in the Middle East and North Africa, a vital part of global energy supply.

Brent crude futures rose 29 cents to $115.99 a barrel at 1130 GMT, having fallen to as low as $115.21. Prices have risen in four out of the past five sessions but dropped from the near $120 hit in late February.

U.S. crude futures gained 40 cents to $105.37.

Volumes for both contracts were moderate as high volatility in recent weeks on the oil market has sent some investors to the sidelines and others into safer havens.

In Yemen, a small oil and gas producer, opposition groups called on protesters to march on President Ali Abdullah Saleh's Sanaa palace on Friday to demand he step down, hoping to end a crisis his allies abroad fear will benefit Islamic militants.

Yemen is a very hot topic now. It is not that important to the oil market but unrest in the region gives enough psychological support to prices, Andy Sommer, energy market analyst with EGL, said.

Seven weeks of street protests against Saleh's 32-year rule of the impoverished Arabian Peninsula state has raised alarm in Western capitals at the prospect of a country where al Qaeda has entrenched itself falling apart.

Its neighbor Saudi Arabia is the world's top oil exporter and the only OPEC member nation with enough spare capacity to compensate for supply disruptions elsewhere.

The civil unrest has spread across oil rich North Africa and the Middle East to such countries as Tunisia, Egypt and Bahrain and has shut in the bulk of Libya's oil output.

While this transition is going on, it can only threaten oil supplies and increase uncertainty - both things that will keep oil prices strong, said Christopher Bellew at Bache Commodities.

Western warplanes silenced Muammar Gaddafi's artillery and tanks besieging rebel-held Misrata in western Libya on Wednesday after a U.S. admiral warned his armor was the next target.

Breathing defiance, Gaddafi earlier said Western powers who carried out a fourth night of air strikes on Libya to protect civilians under a U.N. mandate were a bunch of fascists who will end up in the dustbin of history.

Buried by Yemen and Libya, protests in Syria continued and conflicts in the Gaza strip were escalating.

Palestinian rockets struck two cities deep in Israel on Wednesday, wounding a resident and prompting a deputy to Prime Minister Benjamin Netanyahu to call for a new offensive against the Hamas-ruled Gaza Strip.

In West African oil producer Nigeria, some violence has been reported ahead of presidential election in April.

Some lid on prices came from the United States, the world's second-largest energy consumer. Analysts expected government data to show a 1.6 million barrel increase in the week to March 18 when it is released later in the day.

Global markets were also watching a key vote on austerity measures in Portugal that could see the country's government brought down. <.EU>

Also of concern is the impact of Japan's earthquake and tsunami. The cost of the damage could top $300 billion, making them out the world's costliest natural disaster.

FTSEurofirst 300 <.FTEU3> index of top European shares were little changed from Tuesday's close, after opening lower. <.EU>

The euro dipped broadly against other currencies.

(Additional reporting by Alejandro Barbajosa; editing by James Jukwey)