At least 11 people have been killed in a gun attack on a church in southern Nigeria, police say.

Up to 18 other worshippers were wounded in the early morning incident at the church in Ozubulu near the city of Onitsha.

There were conflicting reports over whether the attack was carried out by a lone gunman or a group of attackers.

Police said the shooting was the result of a feud between Nigerians from Ozubulu who were living abroad.

Anambra State Police Commissioner Garba Umar said the violence could be linked to drug-trafficking.

He said the gunman had been hired to kill a local man who was believed to be in St Philip's Catholic Church.

One of the Nigerian expatriates involved in the feud had built the church, Mr Umar added in a statement.

Parish priest Jude Onwuaso said that a "boy or man" entered the church and started shooting:

"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 there was more than one attacker and they had been targeting the son of a local chief.

They had not found him at his home and became angry when they could not find him in the church either, Emeka Umeagbalasi told AFP news agency.

The authorities have said they do not believe there was any involvement by the militant Islamist group Boko Haram, which has burned hundreds of churches during its insurgency in the north-east of the country.