A bomb attack at a packed new Catholic church in northern Tanzania has killed one person and injured at least 30 people, police say.
The blast happened on Sunday in the town of Arusha, where the Vatican's ambassador to Tanzania, Archbishop Francisco Montecillo Padilla, was attending the official opening of the church. He escaped unharmed.
Witnesses said at least one person had been trampled to death in the stampede after the blast.
"There have been 30 people wounded, three in a serious condition, and one person has been arrested," Liberatus Sabas, the regional police chief, said.
It was not immediately clear what caused the explosion.
Arusha is a town popular with tourists visiting the nearby Serengeti national park and snowcapped Mount Kilimanjaro.
"This is a sad day, our security forces are mobilised, and the culprits will be arrested and brought to justice," Magesa Mulongo, Arusha's commissioner, said.
"For the time being we don't know if it is a bomb."
If a bomb blast is proven, it will mark an escalation in sectarian tensions in East Africa's second biggest economy.
Tensions have been high between Tanzania's Christian and Muslim communities in recent months, and local member of parliament Godbless Lema condemned the blast as the work of "criminals".
Last month, in the far south of Tanzania, police fired tear gas to disperse around 200 Christians rioters attempting to torch a mosque over an argument over who should be allowed to slaughter animals.
In February, a Catholic priest was shot dead outside his church on the largely Muslim archipelago of Zanzibar, the second such killing in recent months.
A church was also set on fire on Zanzibar in February.
"Religious fundamentalism is a reality in this country, but the government does nothing," Lema said angrily outside the church, as police cordoned off the area and ordered people away from the building.
The newly built church, in the Olasti district on the outskirts of Arusha town, was celebrating its first ever mass when the blast took place, and people were squeezed into the church building as well as sitting on benches outside.
"When it exploded there was a stampede, people running in all directions, walking on each other, children were screaming and women crying," said Viviana, who was helped out of the church by her son.
"I saw a dead woman trampled, I think even her two children were killed in the same way," said a woman, who gave her name only as Mariana.
An AFP reporter said that several wounded people were taken to hospital, and that police had closed off roads around the church.
Worshippers angrily accused the police and the government of failing to properly protect them.
"There were so many people, the church was full, and the faithful were sitting on benches outside - it was a great day of celebration," said Jacob, a motorcycle taxi driver, who had been at the mass.
Bernard Membe, Tanzanian foreign minister, said in a message on Twitter that he was "greatly shocked" at the news of the blast.