Hundreds of Sudanese troops arrived in Yemen’s southern port city of Aden on Saturday, the first batch of an expected 10,000 reinforcements for the Saudi-led coalition fighting the country’s Shiite Houthi rebels, security officials said.

The troops’ mission is to secure Aden, which has seen an uptick in drive-by shootings of pro-government troop leaders and officials as extremists became more entrenched in the city in recent weeks, the pro-government security officials said.

Yemen’s fighting pits the Houthis and allied army units against forces loyal to the coalition-backed internationally recognized government as well as southern separatists and other militants.