The Khartoum government has blocked South Sudanese oil exports through its Red Sea port due to a dispute over transit fees, Oil Minister Ali Ahmed Osman said on Monday.

"Sudan stopped South Sudan's exports of oil on November 17," in the second such incident since August, a month after the south declared its independence, the minister told reporters.

"After the independence of South Sudan, we allowed them to export oil and we asked them to pay the fees of the port and some other fees, which they agreed to," he said.

"Up to the end of October, the total amount of fees owed is $727 million and they haven't paid anything. For this reason, we decided to stop South Sudan from exporting oil," said Osman.

He explained that the pipeline had not been shut down but the south was not being allowed to ship its oil cargo out of Port Sudan.

In August, a southern oil cargo was briefly detained at Port Sudan, also because of the row over duty payments, before being allowed to sail.

Khartoum said the authorities in Port Sudan, the landlocked south's only export terminal, had blocked a 600,000-barrel southern oil cargo after Juba refused to pay the duties.

The two sides said at the time that no agreement had yet been reached between north and south on transit fees, one of the most sensitive of divided Sudan's unresolved issues.

North and South Sudan both depend heavily on their oil receipts.

Just weeks before the south seceded, President Omar al-Bashir threatened to deny Juba access to the north's oil infrastructure -- its pipelines, refinery and export terminal -- if no deal was reached prior to partition.

South Sudan’s government said last week that its oil production has fallen 20,000 barrels per day.

"The production at the moment is like, 350,000 per day," Petroleum and Mining Minister Stephen Dhieu Dau said, attributing the decline to an exodus of skilled Sudanese staff and closed borders with the north blocking supplies.

The newly-independent country, which seceded from the north in July, is one of the world's poorest and depends on oil for 98 percent of its income.