Oil prices rose to a one-month high in Asia today - to above $30 a barrel - amid fresh supply fears sparked by plans for a general strike in Nigeria and storms off the coast of Mexico.
In addition, increased tensions in the Middle East after Israel launched an air raid into Syria in reaction to a suicide bombing provided underlying support, oil brokers said.
Benchmark November crude, quoted on the New York Mercantile Exchange, was up three cents at $30.43 per barrel, building on a 56-cent rise on Friday.
Nigeria's main trade union called on Saturday for a general strike to start on Thursday to protest against a rise in fuel prices in the world's seventh-biggest oil exporter.
President of the Nigeria Labour Congress (NLC), Mr Adams Oshiomhole, said "the first phase of the strike will last two weeks", raising fears oil production could be affected.
Nigeria's two main oil unions have given the government one week to clarify its position on fuel price deregulation and have said they might join any action called by the NLC.
Two hurricanes are also hovering off Mexico's Pacific coast on Sunday, and a tropical storm lashed Mexico's Gulf coast, keeping two oil shipping ports shut due to intense rains and pounding waves.
Traders said Middle East tensions escalated over the weekend after Israel launched its deepest air raid into Syria in 30 years, attacking what it said was a training camp for Palestinian militants.