Yemeni security officials and witnesses say Saudi-led coalition airstrikes targeting Shiite rebels have resumed in the southern port city of Aden after the end of a five-day humanitarian ceasefire.

The ceasefire expired at 11 p.m. Sunday (2000 GMT, 4 p.m. EDT), and the coalition airstrikes hit rebel positions and tanks in several neighborhoods of Aden, the officials said. Officials spoke on condition of anonymity because they were not authorized to speak to the media, and the witnesses requested anonymity because they feared reprisals.

Since late March, Saudi Arabia has led airstrikes against the Shiite Houthi rebels and allied military units loyal to former President Ali Abdullah Saleh. The air campaign is aimed at weakening the Houthis and restoring ousted President Abed Rabbo Mansour Hadi, who fled the country in March.