New York's main contract, West Texas Intermediate for delivery in September, was up 32 cents at USD 107.17 a barrel in mid-morning trade, and Brent North Sea crude for September gained 39 cents to USD 110.59.
"Developments in Egypt are on centre stage again and will continue to apply upward pressure on oil prices," said Sanjeev Gupta, head of the Asia-Pacific Oil and Gas Practice at consultancy EY, formerly Ernst and Young.
Egyptian security forces stormed the Cairo protest camps of ousted Islamist president Mohamed Morsi's supporters in an assault yesterday.
Traders fear the bloody unrest in Egypt could hit crude shipments through the Suez Canal and Sumed Pipeline, which provide a link between Europe and Asia and allows ships safer and faster travel between the regions without having to sail around Africa.
While Egypt is not a major oil producer, the Suez canal carries about 2.5 million barrels daily, roughly equal to eight per cent of the output of cartel OPEC.
Prices also gained support from a decline in US crude stockpiles, indicating firmer demand in the world's largest economy.