The human rights charity Amnesty International has joined calls for Nigeria's government to halt the sale by Shell of its onshore oil business in the country - unless human rights in the Niger Delta are protected.

The charity says the proposed sale risks worsening human rights abuses if the pollution caused by the oil company is not addressed.

It says Shell must provide sufficient funds to clean up the environmental damage it's caused and that local communities be consulted on the sale, worth more than $2.4bn (£2bn).

Activists blame Shell for frequent oil leaks in the Niger Delta that among other problems have led to the contamination of ground water sources.

Nigeria's government has not commented.

Shell has previously promised that the new owners would deal with the damages.