Libya’s navy barred an oil tanker from loading crude at an eastern port controlled by a mutinous militia, a day after officials reopened the western oilfield of el-Sharara shut down by protesters for more than two months, as the fragile government attempts to gain control over its most lucrative resource.

The state-owned National Oil Corporation on Monday issued a statement saying Libyan armed forces prevented a Malta-flagged tanker from entering the port of Es Sider. It also warned customers over the weekend against purchasing oil from the militia, which controls the Ras Lanuf, Es Sider and Zueitina ports in eastern Libya and has demanded autonomy for the country’s east before relinquishing them.

“It is relatively easy for the government to meet the demands of protesters in the west of Libya because they are not seeking autonomy,” said Amrita Sen, an analyst at Energy Aspects in London. “But the situation in the east is worsening – and that is a major concern for the market.” […]