Stock prices on Wall Street were slightly positive, while the euro traded roughly flat, rebounding from earlier weakness.
Oil prices have traded in concert with equities for most of this year. A weakening dollar against the euro has also made greenback-denominated oil more affordable for buyers using the single currency.
"Oil is very much distracted by macro events today, gauging the sentiment in broader markets and taking its lead from that," said Matthew Smith, director of commodity research at the New York-headquartered Clipper Data.
At least 30 people were killed in attacks on Brussels airport and a rush-hour metro train in the Belgian capital, according to public broadcaster VRT, triggering security alerts across Europe and bringing some cross-border traffic to a halt.
Oil prices had also been pressured by Libya's decision not to attend a gathering in Doha next month intended to help OPEC and other major oil producers cut a deal to keep output at January's levels.
Despite the latest price action, some traders and analysts cautioned of possible profit-taking ahead after oil's huge rally since February amid marginal improvements in supply-demand.
U.S. crude's new front-month contract hit a 2016 high of $41.90 earlier on Tuesday on reports of the first drawdown in inventories at the Cushing, Oklahoma delivery hub for U.S. futures since January.