At least 11 people have died and several more were wounded in a church shooting in southern Nigeria on Sunday.

The early morning incident in Ozubulu, near the city of Onitsha, was the result of a feud between local Nigerians who were living abroad, police said, and left 18 injured.

Anambra State Police Commissioner Garba Umar said the violence could be linked to drug trafficking but there were no signs Boko Haram, the Islamist militant group targeting hundreds of churches in northern Nigeria, was involved.

Umar said a gunman had been hired to kill a local man believed to be in St Philip's Catholic Church, with other local media reports suggesting the killing was the result of a conflict between two sons.

Differing reports make it unclear whether the attack was carried out by a lone gunman or by a group but one of the men involved built the church, the police statement said.

'Such conduct shows the people behind the act do not fear God,' Umar added.

Parish priest said a 'boy or man' had come into the church and opened fire.

'After the first round, there was second round and I guess it was during the second round that people were shot dead. When I came back I discovered that some of my parishioners were dead, about five or six I saw shot dead bleeding.

'A lot of people were injured, some were shot in the stomach, some were shot in the head and some were shot in the hand.'

But a local human rights activist said more than one attacker was involved and they were targeting the son of a local chief.

Emeka Umeagbalasi told AFP news agency that after they couldn't find him at his home or at the church they became angry and opened fire. 

Police vowed to find all those involved.