The United Arab Emirates says three of its citizens are in custody in Tanzania in connection with a church bombing that killed two people and injured more than 50 others.

The UAE Foreign Ministry did not make clear whether the three were additional suspects in Sunday's attack in the northern city of Arusha, but it suggests they are among four alleged attackers originally identified as Saudis.

Wednesday's statement said the three men were being held in Dar es Salaam.

A total of six people have been arrested in the bombing, which occurred just before the Roman Catholic church's inaugural Mass.

The reason for the attack is still unclear, but Tanzania has been hit by sectarian violence between Christians and Muslims.