Oil prices fell to a four-year low on Tuesday (4 November), close to $82 a barrel, as the world's top producer Saudi Arabia cut prices to the United States.
Front-month Brent crude, an industry benchmark, fell to $82.08, its lowest price since October 2010, before recovering to $82.53 by midday in London.
Opec-member Saudi Arabia boosted December sales prices to both Asia and Europe but reduced prices to the smaller US market.
Some analysts detected a political motivation behind the Saudis' price cut, suggesting that the Kingdom is seeking to protect its market share in the US by targeting US shale oil producers.
The move "signalled Saudi Arabia's intention to fight for US market share and could even show its intention to squeeze US shale producers," said Daniel Ang of Phillip Futures, in a note.
US crude producers have continued to boost production throughout 2014, leading to a supply glut in the market. Stocks look likely to have risen again last week, which would be the fifth weekly increase in a row, if confirmed.
While the US companies have been banned from exporting crude oil for four decades, a movement to allow sales abroad has gathered momentum in recent months.
However, other analysts urged caution in suggesting the move marked the start of a price war.
"We would strongly advocate against interpreting every month's OSP publication in the context of 'price war' and 'market share battle' stories," said JBC Energy in a note.
Opec, the global cartel of oil exporters that includes Middle Eastern countries as well as Venezuela and Nigeria, has shown few signs it will reduce oil production ahead of its meeting in Vienna on 27 November.