The officials, speaking on condition of anonymity because they were not authorised to speak to reporters, say two civilians were killed today in both Aden and Marib, while one died in Taiz.
Among the heaviest fighting today is in Marib, home to much of Yemen's oil industry, where battles are raging between militias supporting Yemen's embattled president and Shiite Houthi rebels, the officials say.
Meanwhile, United Nations Special Envoy to Yemen Ismail Ould Cheikh Ahmed held consultations with Yemeni political groups in the capital, Sanaa, after peace talks were indefinitely postponed earlier this week.