DUBAI, Dec 16 (Reuters) - Saudi-led air strikes hit positions of the Iran-allied Houthi group in two conflict zones in Yemen on Wednesday, residents and tribal sources said, despite the start of a seven-day ceasefire on Tuesday coinciding with peace talks in Switzerland.

"Coalition planes launched an air strike on the positions of the Houthis and Saleh forces in the Najd area of Sirwah district after they repeatedly violated the ceasefire," a tribal source said by telephone from the central province of Mareb.

Residents in the southwestern city of Taiz also reported an air strike there after Houthi forces launched rockets on the area, and Saudi state news agency SPA said the Houthis killed one of its officers in a border area after the ceasefire began. (Reporting by Mohammed Ghobari; Writing by Noah Browning; Editing by Catherine Evans)