Dozens of worshippers are feared dead after an attack on a Catholic church in Nigeria.

Multiple suspects opened fire and detonated explosives at the start of a busy Sunday service in the south-west state of Ondo, according to local media.

Videos showed bloodied bodies on the floor of Owo’s Saint Francis Catholic Church. Some parents had died while holding their children.

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No group has claimed responsibility and police are investigating the motivations, including whether it was a terrorist attack.

One of the armed suspects was tackled to the ground after being spotted holding a firearm in the street, according to witnesses.

State police spokesman Funmilayo Ibukun Odunlami said early on Monday morning (Australian time) “there was an incident” and police would issue a statement soon.

Africa’s most populous country has witnessed attacks and kidnappings for ransom by armed gangs, mostly in its north-west. Such attacks are rare in south-western Nigeria.

Nigerian President Muhammadu Buhari condemned the “heinous” murders.

Ondo governor Arakunrin Oluwarotimi Akeredolu said he was heading back to the state from the capital Abuja after the “unprovoked attack and killing of innocent people of Owo.”

“We shall commit every available resource to hunt down these assailants and make them pay,” he said in a statement, calling the assault “vile and satanic”.

-with AAP