The US government is offering $27m in rewards for information on the whereabouts of six leaders of the Somalia-based Al-Shabaab group.

The highest reward is $6m for the group's leader Abu Ubaidah.

He replaced Ahmed Abdi Godane, who was killed in a US drone strike last year.

Among those being hunted is Mahad Karate, also known as Abdirahman Mohamed Warsame, believed to be a key player in the attack on a Kenyan university which killed 148 people.

The Islamist militant group is battling the UN-backed government in Somalia.

The rewards

• $6m for Abu Ubaidah also known as Direye, named Al-Shabaab leader in September 2014
• $5m for Mahad Karate, also known as Abdirahman Mohamed Warsame, accused of playing key role in Garissa University College attack
• $5m for Ma'alim Daud who the US thinks is responsible for Al-Shabaab's recruitment and training
• $3m for Maalim Salman who the US says he has been involved in operations in Africa targeting tourists
• $3m for Ahmed Iman Ali who the US believes to have recruited Kenyans