(CNN) -- U.N. Secretary-General Ban Ki-moon has urged Ukrainian government forces and rebel fighters to respect a fragile ceasefire following the death of a Swiss Red Cross worker in shelling in eastern Ukraine. The humanitarian worker, identified as Laurent DuPasquier, 38, by the International Committee of the Red Cross, was killed when a shell landed near the ICRC building in the city of Donetsk. Ban said he was "saddened and disturbed" to learn of the death, which came a day after 10 civilians were killed in the shelling of a Donetsk school, according to the Organization for Security and Cooperation in Europe.
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NEW: Russian foreign minister urges rebels, Kiev to maintain the ceasefire
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U.N. chief warns warring sides to respect ceasefire after "dangerous surge in fighting"
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A Red Cross worker from Switzerland was killed in shelling in Donetsk
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Kiev blames rebels for the shelling, while Moscow points finger at Kiev authorities
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