Sudan's President Omar al-Bashir has ordered the closure of all pipelines carrying oil from South Sudan.
Bashir told public rally in the capital Khartoum on Saturday that the move was in response to South Sudan's funding of rebels fighting his regime.
He ordered the stoppages to begin Sunday.
Bashir had warned last month that he would block the oil if the South Sudan's government provides assistance to rebels fighting in South Kordofan and Blue Nile states, or in the Darfur region. Juba has denied supporting rebels.
Land locked South Sudan must export its oil to international markets through pipelines owned by Sudan that run through its territory.