Investors already were focused on supply during the session as fighting in oil-rich Libya threatened to disrupt exports. Eastern forces were advancing on the country's capital, disregarding global appeals for a truce.
"The violence in Libya is captivating the market," said John Kilduff, a partner at Again Capital in New York. "Given the intense efforts of Saudi Arabia and other countries to restrict output, there is a sense that losing the Libyan oil, again, has the makings of a supply crunch."
To prop up prices, OPEC and allies such as Russia pledged to withhold around 1.2 million barrels per day of supply from the start of this year. The group, led by Saudi Arabia, has exceeded those expectations so far this year.
"OPEC's ongoing supply cuts and U.S. sanctions on Iran and Venezuela have been the major driver of prices throughout this year," said Hussein Sayed, chief market strategist at futures brokerage FXTM.
"However, the latest boost was received from an escalation of fighting in Libya which is threatening further supply disruption," he added.
Strong U.S. jobs data on Friday also still supported markets on Monday.
Despite the factors boosting prices, there are still factors that could bring oil prices down later this year.
Russia is a reluctant participant in its agreement with OPEC, and Kirill Dmitriev, the head of Russia's direct investment fund, said OPEC and its allies should raise output from June. Dmitriev previously said it was too early to pull back from cuts.