A man raised in San Diego has become a leader of one of Africa’s deadliest terror groups and the highest-ranking U.S. citizen fighting with foreign terrorists, federal authorities said Monday.

Jehad Mostafa. FBI

Prosecutors in California disclosed the allegations against Jehad Serwan Mostafa, 37, by unsealing an indictment accusing him of providing critical support to the East African terror group al-Shabab.

Mostafa was indicted in 2009 on similar crimes, but he has remained at large — even after a $5 million reward for his arrest and conviction was offered, the United States Attorney’s Office for the Southern District of California said in a news release.

The charges announced Monday allege that he now plays a critical role in al-Shabab, which promotes an Islamic state and has killed thousands of people since its founding in 2006.

One of the group’s deadliest attacks targeted the Westgate shopping mall in Kenya that killed 60 people in 2013. Earlier this year, the group claimed responsibility for killing 21 people in an attack on a hotel in Kenya's capital, Nairobi.

Authorities said that Mostafa grew up in the Serra Mesa neighborhood of San Diego, where he attended high school and college. He left in 2005, traveling first to Yemen, then Somalia, where he is now thought to be, authorities said.

Mostafa is accused of helping train soldiers, working in media operations, planning attacks on the Somali government and African Union forces, and helping lead the group’s explosives department, prosecutors said.

In September, the group claimed responsibility for an attack that targeted an American military base in Somalia.

No American soldiers were injured and the military said it killed 10 fighters in a retaliatory strike.