South Sudan's defence minister has been killed along with at least 21 other people in a plane crash in the south.
Dominic Dim Deng was returning with a military delegation to the regional capital, Juba, from a political conference in the town of Wau.
A presidential adviser was among the passengers and crew members killed.
South Sudan's President Salva Kiir said engine trouble had caused the crash, about 400km (250 miles) west of Juba. He declared three days of mourning.
The BBC's Amber Henshaw in Sudan says the incident will bring back memories of the death of South Sudan's first leader, John Garang, who was killed in a helicopter crash three years ago.
His widow called his death an assassination, despite an official probe that blamed pilot error.
Philip Yona Jambi, South Sudan's rural development minister, said that the pilot asked permission to make a crash landing in Rumbek after reporting engine trouble.
"Unfortunately they couldn't make it to Rumbek - the plane just blew up and all passengers died," he told the BBC's Focus on Africa.
He said passengers on board included Mr Deng and his wife, senior presidential adviser Justin Yak and his wife, and other senior military officials.
Our correspondent says officials have arrived at the site of the crash and the United Nations has also sent a helicopter to the scene.
Mr Kiir, who is also Sudan's vice-president, told journalists in Juba that it was a very sad day for South Sudan.
He said that the control tower in Rumbek had lost all contact with the plane not long after the pilot had requested permission to land.
Mr Jambi said that the news had shocked many southern Sudanese.
"People are very worried and those who have heard about it will suspect foul play because John Garang died in a crash and they still don't believe the results of the investigation," he said.
Mr Garang died not long after the region signed the 2005 peace deal which ended decades of war with Khartoum.