A highly sought after al-Shabab leader with a $3m bounty on his head has surrendered to government and African Union forces, a Somali intelligence officer has said.

Zakariya Ismail Ahmed Hersi surrendered to Somali police in the Geddo region where Somalia borders Kenya and Ethiopia, the officer said.

"Zakariya Ahmed was a very senior person who worked with Godane," said regional military official Jama Muse, referring to former al-Shabab leader Ahmed Abdi Godane, who was killed by a US air strike in September.

"He was in charge of intelligence and finances. He was one of the senior al-Shabab commanders who the Americans put a lot of money on their head," he added.

An al-Shabab media spokesman told Al Jazeera that Hersi had left the group two years ago and that he was then a mid-level commander - not an intelligence chief as claimed by Somali officials..

Military official Mohamed Osmail said Hersi was hiding in a house in a border town, and made contact with government officials in order to hand himself in.

Another intelligence source said the surrender was believed to have been motivated by a series of recent bloody splits and purges within the group, with Godane having ruthlessly eliminated many of his rivals and his successor, Ahmad Umar Abu Ubaidah, continuing to maintain strict internal security.

Hersi was one of eight top al-Shabab officials whom the US administration offered a total $33m in rewards for information leading to their capture in 2012.

Despite suffering major losses such as losing major cities, al-Shabab remains a threat in Somalia and Kenya.

While the government offered an amnesty to al-Shabab members in September, none of the key leaders of the group has so far taken up the offer.