Two Sudanese health ministry workers helping to vaccinate children in the Darfur region have been killed, the United Nations said on Saturday, condemning the incident.
The victims, a vaccinator and a driver, were part of a team inoculating vulnerable children against measles in West Darfur state, Ali Al-Za'tari, the UN's chief in Sudan, said in a statement.
It did not say exactly how they died, or when.
"I call on all parties to ensure the protection of all personnel working to deliver assistance to populations in need throughout Sudan," Za'tari said.
Violence has worsened in Darfur, where at least 460,000 people have been displaced by fighting this year, the United Nations says.
While battles between the government and rebels continue, Defence Minister Abdelrahim Mohammed Hussein said this month that violence between Darfur's various tribes has eclipsed rebel activity as the main security threat.
The fighting, largely between Arab groups over land and other resources, has involved heavy weapons including rockets.
Non-Arab rebels rose up 10 years ago in Darfur, seeking an end to what they viewed as Arab elites' domination of Sudan's power and wealth.
In response, government-backed Janjaweed militiamen shocked the world with atrocities against civilians.
Analysts say the cash-starved Khartoum government can no longer control its former Arab tribal allies, whom it armed against the rebellion.
Government-linked militia and paramilitary groups are suspected of carrying out many kidnappings, carjackings and other crimes in the region.