A Kenyan official says a drone strike in Somalia is believed to have killed a senior member of the al-Shabab extremist group who allegedly helped plan the 2013 Westgate Mall attack in Nairobi.

The official said Thursday that Adan Garar and two others are suspected to have been killed after their car was targeted near the town of Bardhere. The official declined to say which country the drone belongs to.

The senior official, who insisted on anonymity because he wasn't authorized to give the information to the media, says Garar is also suspected of planning failed attacks on Kenya's coast and in the Ugandan capital, Kampala, last year.

Sixty-seven people were killed in the Westgate attack which was carried out by four gunmen from al-Shabab.