Hiiraan Online

Nine suspects were arrested following the May 5 explosion in Arusha, police said, including five Tanzanians, three Emiratis and a Saudi.

The four foreigners have been released without charge and left Tanzania, according to media in their respective countries.

"Investigations conducted by detectives and in collaboration with other specialists such as the FBI and Interpol showed that the foreigners had no connection with the attack," said Arusha's police chief Liberatus Sabas.

The attack was one of the worst such incidents to hit the east African country in years.

One of the five Tanzanian suspects, Victor Ambrose "was brought before a court and charged with murder and attempted murder" on Monday, Sabas said in a statement.

"The interrogation of other suspects continues," he added, noting a police reward of $30,000 (23,000 euros) for information.

In addition to the three people killed in the blast, more than 60 people were injured when attackers hurled a bomb into the compound of the newly built Saint Joseph's Roman Catholic church. Sabas said that 31 people remained in hospital.

The bomb attack, which no group has claimed, was described by Tanzanian President Jakaya Kikwete as "an act of terrorism".

Officials have given no indication as to who might have carried out the attack, but tensions have been high between Tanzania's Christian and Muslim communities in recent months.

Around half of Tanzanians are believed to be Christian, and around a third Muslim, although there are no official figures.

In neighbouring Kenya -- whose troops invaded southern Somalia in 2011, prompting warnings of revenge by the Al-Qaeda linked Shebab insurgents -- several churches have been targeted in attacks similar to the Arusha blast.

While Tanzania does not have troops in Somalia, it is home to Islamist groups connected to radical groups in the wider region including the Shebab, according to United Nations experts.