A Red Cross worker has been killed in eastern Ukraine.
The worker died when a shell landed near the group's office in Donetsk, one of the main rebel-held cities in the east.
The International Committee of the Red Cross (ICRC) identified the victim as Laurent DuPasquier, a 38-year-old Swiss national who had arrived in Ukraine just six weeks ago.
In a statement, Dominik Stillhart, the Geneva-based organization's director of operations, condemned the incident, saying "indiscriminate shelling of residential areas is unacceptable and violates international humanitarian law."
Government forces and the pro-Russian rebels blamed each other for the October 2 shelling.
Ukrainian Foreign Minister Pavel Klimkin wondered whether the "terrorists have any idea of what humanity is all about when they shell the Donetsk office of the ICRC, whose only aim is to help people?"
Rebel leader Andrei Purgin said the Ukrainian government forces shelled Donetsk constantly and that the attack had come from one of their areas.
"The Red Cross worker was killed by a rocket from a multiple-rocket launcher," he told Reuters.
The incident will bring fresh strains to an already shaky cease-fire that has been in force since September 5.
Seven Ukrainian soldiers were killed in a single strike by tank fire on their armored personnel transporter on October 1.
That same day, at least 10 people were killed when shelling hit a school playground in Donetsk and a public transit minivan in a street nearby.
Meanwhile, a top U.S. official has accused Moscow of continuing to supply the rebels with weapons despite the cease-fire.
State Department Assistant Secretary of State for European and Eurasian Affairs Victoria Nuland was speaking on October 2 at the U.S.-Central Europe Strategy Forum in Washington.
Nuland added, "There is not a military solution to this if the Russian Federation chooses to go in and flatten Ukraine, because the Russian military is always going to be larger."
Moscow denies sending troops or weapons to the rebels.
With reporting from AP and Reuters