KAMPALA, Uganda –– Ugandan President Yoweri Museveni was elected to a fifth term, officials said Saturday, extending his 30-year rule over the East African nation in an election marked by opposition arrests and international concern over its credibility.

The former guerrilla commander won 60.75 percent of Thursday’s vote. Opposition candidate Kizza Besigye was second with 35.37 percent, Electoral Commission Chairman Badru Kiggundu said Saturday in the capital, Kampala.

Turnout in the presidential and legislative elections was 63.5 percent, Kiggundu said. Voting took place in heavy security. Besigye is under house arrest after police stormed his party headquarters when he was accused of planning to announce his own vote tally, and some social media were blocked. The moves were criticized by the U.S. and European Union.

Museveni’s re-election indicates a trend in Africa, where a growing number of leaders are trying to extend their rule, in some cases amending their countries’ constitutions to do so. Museveni is one of the continent’s longest serving presidents.

The results show a decline in support for Museveni since his 2011 re-election. According to Uganda’s constitution, he would be too old at 71 to run again in five years.

Uganda’s $27 billion economy has foreign companies developing its estimated 6.5 billion barrels of oil resources. And, Uganda is Africa’s biggest coffee exporter.

Uganda plays a prominent role in the region, contributing troops to the African Union campaign fighting al-Qaida-linked militants.

The U.S., which has described Uganda as a key strategic partner, expressed concern over Besigye’s detention and the harassment of opposition party members.