Police in Nigeria say they are tracking down gunmen who killed at least 12 people, including a pregnant woman and her four children, in the south-eastern state of Anambra.

The police have blamed the increasing violence in the region on Biafra separatists.

A community leader told the BBC that the pregnant woman and her children were returning home on a motorcycle taxi when gunmen ambushed them in the Orumba area.

Several other people were also shot dead in separate incidents on Sunday evening. Police say they are investigating.

The killings have sparked outrage on social media.

They happened a day after mutilated bodies of a local politician and his aide were discovered a week after they were abducted.

The worsening violence in south-eastern Nigeria is being blamed on a banned separatist group – the Indigenous People of Biafra (Ipob) – which is campaigning for a breakaway state in the region.

The group has denied involvement in some of the attacks.

Security forces are also grappling with various armed groups carrying out killings and kidnappings in other parts of Nigeria.

In the north-east of the country, more than 30 people were reported either killed or kidnapped in an attack in Borno state last Sunday.

Militants from Boko Haram and an IS-linked group are active in that region.

The widespread insecurity is a major concern ahead of elections due to take place in February next year.