A British man is among four people arrested by authorities in a disputed area in Sudan, the Foreign Office confirmed today.
Sudanese officials said the four - a Briton, Norwegian, South African and South Sudanese - were detained in the sensitive Heglig oilfield area, on the border between Sudan and South Sudan, which became an independent state in July 2011.
However since then tensions between the new country and the state it seceded from have been rising - with fears that there could be a war within weeks.
A Foreign Office spokesman said: "We are urgently investigating the arrest of a British national in Sudan.
"We immediately requested consular access and stand ready to provide further consular assistance."
Sudan's army spokesman said the men had military hardware and an armoured vehicle in their possession, Associated Press reported.
Colonel Sawarmi Khalid Saad said on state television yesterday that the four had military backgrounds and were carrying out military activities in Heglig.
The oil-rich region was captured by South Sudanese troops earlier this month. Sudan later said it took it back.
Col Saad said the arrests of the four supported claims by the Khartoum government that South Sudan used "foreigners" when it captured Heglig.