SANAA, Yemen – A new truce in Yemen was pierced within an hour as Saudi-led airstrikes hit targets in the capital Sanaa and the southwestern city of Taiz following reports of ground movement and fighting, security officials said.

The U.N.-declared truce that began after midnight Friday is meant to last through the end of the holy month of Ramadan and allow in desperately needed humanitarian aid for millions of people.

Houthi rebel media reported at least one airstrike in the east of the capital of Sanaa, targeting a military camp used by the rebels. It was not clear what immediately prompted the airstrike.

Security officials said three airstrikes came after Shiite rebels and their allied forces clashed with rivals who have held pockets of resistance against the rebels’ control of Taiz.

Witnesses also reported the airstrikes. One airstrike targeted a military camp used by forces loyal to the rebels, while another hit a rebel convoy, the officials said.

Both sides exchanged blame for violating the truce. Rebel officials said their rivals were using the truce to advance in Taiz. Fighters accused the rebels of trying to push them from the territories they hold.