Serour al-Wadie of the Salafi movement said today that the rebels shelled their district in Damaj, in Saada province.
Animosity runs deep between the Salafis and the Hawthis, rebels from a branch of Shiite Islam fighting against the government.
Each camp has been accusing the other of breaching a fragile two-day government-brokered ceasefire.
Defense Ministry officials said a UN envoy to Yemen, Jamal Benomar, was in contact with both camps to end the fighting.
Since Wednesday, at least a hundred people have reportedly died in fighting between the two groups.