Oil prices strengthened on Monday as an attack on an oil pipeline pumping station in the Caspian Sea slowed flows from Kazakhstan, while investors monitored developments of a possible Moscow-Kiev ceasefire agreement that could ease sanctions and increase global supplies.

Oil futures were lifted Tuesday, ending with gains after a drone attack by Ukraine on a pipeline carrying crude from Kazakhstan across southern Russia curtailed flows.

A Ukrainian drone attack on a major oil pipeline in southern Russia could reduce export volumes by almost a third over the next two months, Russia's state pipeline operator said Tuesday. On Monday, explosive-packed drones hit a pumping station of the Caspian Pipeline Consortium,

The Deputy Chairman of Russia’s powerful Security Council, Dmitry Medvedev, on Tuesday said that Ukrainian drones had attacked a pipeline in Russia which pumps about 1% of global crude supply. Medvedev said the strike could disrupt flows to world markets and damage U.