BAUCHI, Nigeria (Reuters) - Unidentified attackers killed more than 30 cattle herders in the northeastern Nigerian state of Adamawa, a police spokesman said on Tuesday. The attack, in the Numan area of Adamawa, began on Sunday night and fighting continued into Monday morning, said Othman Abubakar, a police spokesman for the state, adding that an investigation was underway. He gave no further details. Earlier on Tuesday, a suicide bomber killed 50 worshippers during morning prayers in a mosque in the town of Mubi in northeastern Nigeria, police said, in one of the deadliest attacks in the region in years. 