A Swiss Red Cross worker was killed in eastern Ukraine on Thursday when a mortar bomb struck a building used by the organization, the Red Cross has confirmed.

"One of our colleagues, a Swiss national, was killed in Donetsk, Ukraine, when a shell hit close to our office," ICRC spokesman Ewan Watson told Reuters news agency, not naming the victim.

Blaming the attack on pro-Russian rebels, Ukrainian Foreign Minister Pavlo Klimkin said: "I have only one question: Do 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?"

Fresh fighting at the Donetsk airport was also reported on Thursday, which is held by Ukrainian troops. On Wednesday, at least 10 people were killed by shelling at a school in Donetsk.

EU calls on both sides to observe peace agreement

The European Union voiced concern on Thursday over the recent "tragic deaths."

"We are concerned about the intensification, in spite of the ceasefire in place, of shooting and shelling in eastern Ukraine," a spokesman for the EU's diplomatic service said in a statement.

The EU called on both sides to observe the ceasefire agreement, which was signed by Moscow and Kyiv on September 5: "Observation of the ceasefire is a necessary step for the much-needed restoration of law and order in the east of Ukraine."

The conflict in eastern Ukraine has entered its sixth month and claimed over 3,000 lives. Since the signing of the 12-point peace pact at the beginning of September, nearly 70 Ukrainian soldiers and civilians have been killed, along with an undisclosed number of pro-Russian separatists.

sb/glb (Reuters, AFP, dpa)