(KAMPALA, Uganda)

The Ugandan military confirmed Wednesday that a senior leader of the Lord’s Resistance Army had surrendered in the Central African Republic, a victory for a U.S.-backed offensive that deepens the isolation of the feared rebel group’s top commander, Joseph Kony.

Dominic Ongwen, the group’s most senior commander after Mr. Kony, gave himself up to Muslim rebels in Central African Republic on Sunday before being handed over to U.S. Special Forces, military spokesman Lt. Col. Paddy Ankunda told The Wall Street Journal. The U.S. State Department said Tuesday that U.S. forces in Africa had in custody a man claiming to be Mr. Ongwen.

Col. Ankunda, the Ugandan military spokesman, didn’t say why Mr. Ongwen turned himself in. A military intelligence officer, who declined to be named because he isn’t authorized to speak to the media, said Mr. Ongwen was wounded in battle last year and may have surrendered to seek medical help.

The surrender of Mr. Ongwen now leaves Mr. Kony largely alone at the top of the LRA, one of Africa’s most notorious rebel groups.

In the late 1990s, the LRA tried to topple Uganda’s government to create a state governed by the Bible’s Ten Commandments. Pushed out of Uganda, Mr. Kony’s fighters have moved through several African countries—including the Democratic Republic of Congo and Central African Republic—in a campaign that has killed thousands of people and dragooned children into serving as fighters and sex slaves, according to human rights groups.

Ugandan military officials expressed hope that the surrender of a top commander would soon lead to the capture of Mr. Kony himself, effectively decapitating the LRA’s command structure.

“The pressure on Kony and his fighters is too much,” Lt. Col. Ankunda said. “They have very limited options at the moment.”

Still, Mr. Kony has successfully eluded capture for years. In 2011, the U.S. sent 100 Green Berets to Uganda to help Ugandan-led African Union troops hunt down him and other LRA members. But the fighters soon split into smaller units, and retreated deeper into the jungles.

The surrender of Mr. Ongwen could help the search, said Kasper Agger, a researcher in Kampala for the Enough Project, a U.S.-based group advocacy and research group.

“Given the seniority of his position in LRA, Ongwen must be having some good information on Kony’s whereabouts,” Mr. Agger said.

The State Department in 2013 announced a $5 million reward for information leading to the capture or conviction of Messrs. Kony and Ongwen, as well as Okot Odhiambo, another top LRA leader who has since died.

The International Criminal Court in The Hague issued arrest warrants in 2005 for Mr. Kony, Mr. Ongwen and three other LRA commanders.

It has charged Mr. Ongwen with four counts of war crimes and three counts of crimes against humanity, including enslavement and “inhumane acts of inflicting serious bodily injury and suffering.”

(WALL STREET JOURNAL)