The U.S. State Department is offering a $5 million prize for information leading to the arrest of Jehad Serwan Mostafa, an American citizen on the FBI’s Most Wanted List.

According to U.S. Attorney for the Southern District of California Robert Brewer, Mostafa is believed to be the “highest-ranking U.S. citizen fighting overseas with a terrorist organization.” The thirty-seven year old American is accused of providing material support to the Somali-based terrorist group al-Shabaab.

Born in Wisconsin, Mostafa grew up in San Diego, but then left for Somalia in 2005. It was there that he fought against the Ethiopian intervention in the country and later joined al-Shabaab, which is an al-Qaeda affiliate that seeks to enforce strict sharia law. The group was designated a terrorist organization by the U.S. government in 2008 and has been responsible for numerous attacks in east Africa.

Though Mostafa has been under indictment since 2009, the recent unsealment of an indictment in federal court reveals that this has widened in scope to include allegations brought towards him up to 2017. According to the newly revealed information, he is believed to have been responsible for several attacks in Somalia using improvised explosive devices.

Believed to still be in southern Somalia, Mostafa’s exact whereabouts remain unknown.

Despite being largely absent from the headlines, Somalia remains engulfed in warfare and terrorism. The country continues to suffer from the lack of an effective central government. This has resulted in al-Shabaab using the country as a base for both domestic and regional attacks, such as the one in neighbouring Kenya where it targeted a hotel in the capital of Nairobi.

At the same time, the presence of Islamist militants has resulted in international intervention in the failed state. Among those involved are regional actors like Ethiopia, Burundi and Uganda that act on the behalf of the African Union. Additionally, the United States has carried out numerous airstrikes and on-the-ground special operation missions in the country. According to U.S. Africa Command (AFRICOM), it carried out an airstrike on December 9th that killed a member of al-Shabaab. This followed three previous airstrikes conducted in November.

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This has not stalled al-Shabaab. On the evening of December 10th, the group attacked the SYL Hotel in Mogadishu. The hotel is located near the presidential palace and is a popular hangout spot for both Somali legislators and members of the state security apparatus.

Though it has carried out terrorist attacks abroad and has received foreign volunteers, al-Shabaab has largely kept its focus on Somalia and its immediate vicinity. Unlike other Salafist groups, it lacks global ambitions. This has resulted, in the past few years, in a partial schism with some of the organization’s fighter leaving to support ISIS.