A UN peacekeeper in Sudan's violence-plagued Darfur region has been killed and two others injured, according to a UN statement.
It did not identify the peacekeeper, who died on Sunday, but Ban Ki-moon, the UN secretary-general, extended "heartfelt sympathy and condolences to the government of Sierra Leone", indicating the peacekeeper was Sierra Leonean.
The soldiers came under attack while on patrol in south Darfur.
Ban condemned the attack near Nyala and said he expected the government in Khartoum to "swiftly bring those responsible for this reprehensible act to justice," his spokesperson said.
The attack, which happened on the same day Sudan's President Omar al-Bashir was visiting a newly captured city in the country's south, was not immediately confirmed by Sudanese officials.
The UN-African Union mission in Darfur (UNAMID) said last month that 33 peacekeepers had been killed in Darfur since the force was deployed in 2007 in a bid to halt fighting between rebels and the Khartoum government.
The world body says at least 300,000 people have died since the uprising started in 2003, when non-Arab groups took up arms against the Khartoum government, citing marginalisation. The government puts the death toll at 10,000.
Al-Bashir has been indicted by the International Criminal Court for war crimes and crimes against humanity in Darfur, but he denies the charges and efforts to arrest him have been futile.
He visited Kurmuk in Blue Nile state on Sunday to perform his prayers for the Muslim Eid al-Adha holiday, the country's official SUNA agency reported.
Government troops seized the town from a branch of the Sudan People's Liberation Army North (SPLA-N) on Thursday.
"The rebellion was nothing but a mosquito, which you have now crushed," al-Bashir said, calling on forces to free the whole state from rebels.In another development, South Sudan rejected allegations on Sunday it was arming fighters in Sudan's conflict-stricken border regions of Blue Nile and South Kordofan after Khartoum brought the charges to the UN Security Council.
South Sudan, which became the world's newest country in July after a referendum agreed under a 2005 peace deal with Sudan, has had uneasy relations with its northern neighbour.
Clashes between troops of both countries and militias backed by both sides have led to fears of a wider escalation.
The two countries - which have yet to agree on issues such as how to manage the formerly integrated oil industry - have accused each other of supporting rebellions in their territory.
Khartoum submitted its second complaint to the Security Council this week, accusing South Sudan of supplying anti-aircraft and anti-tank missiles, ammunition, landmines and mortars to the SPLA-N.
"This accusation is false. [We] are not supplying anybody. The north are supporting rebels in the south and they want to cover it up," Philip Aguer, South Sudan's army spokesman, told the Reuters news agency by telephone.
"It should be the other way round. We should be complaining to the Security Council. We don't even have anti-aircraft missiles ourselves."
The SPLA-N forces in Blue Nile and South Kordofan states served as the 9th and 10th divisions of the southern rebel forces called SPLA during the civil war, but the peace agreement placed the areas they fought for in the north.
Many SPLA-N fighters' uniforms still show the flag of the former rebel group that now governs South Sudan.