MOGADISHU, June 16 (Reuters) - Somali Islamist group al Shabaab claimed responsibility on Monday for an overnight attack on the Kenyan coastal town of Mpeketoni that killed at least 50 people, some of them soccer fans at a venue screening World Cup matches.

"Commandos last night carried out a successful raid on the town of Mpeketoni," al Shabaab said in a statement sent to Reuters.