The gains were fueled by hopes of a deal between major non-OPEC producer Russia and OPEC heavyweight Saudi Arabia to reduce production in order to tackle the global supply glut that is weighing on prices.
But Saudi Arabia's response has been lukewarm, despite pressure from other members of the oil cartel that have been hit by low oil prices.
On Sunday, state-owned Al Arabiya television said the kingdom wanted to cooperate with other oil producers to support the market. But it did not give any definite indication that it would reduce output.
Iran, on the other hand, has announced increased production, designed to regain lost market share and revenue due to international sanctions.
For this week's Trader Poll, tell us what's going on with OPEC: