NAIROBI, Kenya (AP) — Kenyan media are reporting that unknown gunmen have attacked the house of Kenya's deputy president moments after he left to campaign with the president for re-election in the Aug. 8 vote.

According to Capital FM Radio, gunmen struck around noon Saturday, attacking police officers guarding the residence of William Ruto in the outskirts of Eldoret, a town 194 miles (312 kilometers) northwest of Nairobi.

It's unclear who the gunmen are but police sources say the siege has ended. Analysts have been worried about violence around the election. The Islamist extremist group Al-Shabab this week threatened to disrupt the vote.

Al-Shabab has carried out more than 100 attacks in Kenya since 2011 in retribution for the country sending troops in to Somalia, where the extremists are based.