Premium petrol and diesel prices up

The three, plus Esso and Susco, also raised diesel prices by 60 satang to Bt42.44 per litre.

The increases follow worries that US oil inventories could fall below 300 million barrels and the weakening of the US dollar against the euro, which forced the West Texas crude oil price up to US$137 (Bt4,600) per barrel on Tuesday. Dubai crude also rose, to $130.74.

Exacerbating the situation is Pakistan's first imports of petrol in six months, with more expected in the next two months.

Salya Sukhonthsub, retail manager for Shell of Thailand, said despite the increases, the marketing margin at Shell remained in negative territory: 40 satang a litre for petrol and 70 satang for diesel.

"Global oil prices shot up this week as Saudi Arabia's plan to raise output could not win the consent of Opec members," he said, adding that the Organisation of Petroleum Exporting Countries claimed oil prices were high due to speculation rather than supply and demand.

European Central Bank president Jean-Claude Trichet called on oil producers to stick to their promise to increase output, saying this was "absolutely essential" to ease supply worries.

Agence France-Presse reported Trichet did not believe speculators should carry most of the blame for higher oil prices that have propelled euro-zone inflation to record highs.

"I'm not sure, frankly speaking, that speculation is the major culprit for what we are observing," he told the European parliament's economic and monetary-affairs committee.

"It seems to be that the major issues are associated with supply and demand."