Kenya’s trade minister is being accused of intimidating one of the largest media groups in Kenya over its exposé of a cooking oil scandal.

The Nation Media Group's investigation looked at how a state agency under the trade ministry reportedly single-sourced private firms to import cooking oil tax-free.

Under Kenyan law, such tax exemptions can only be made for emergency relief goods - with the entire deal potentially leading to the loss of more than $100m (£78m).

The minister, Moses Kuria, lashed out over the report and has banned government agencies from advertising with the media group.

"Nation Media, you must now decide whether you are a newspaper, a broadcaster, a media house or a political party. I have said from tomorrow, even from today, any government department that is found adverting in the Nation Media Group, consider yourself out [of government]," the minister said during a public event.

He followed up the warning in a number of tweets picking out some of the advertisements, while calling journalists at the media house "prostitutes".

His remarks have been condemned by a number of groups, including the Kenya Union of Journalists.

The Media Council of Kenya described them as a threat to press freedom and as soiling Kenya’s global image.

Kenya's anti-corruption commission said no public institution or official should be victimised for doing business with Nation Media Group as public procurement was governed by the law.