A Yemeni colonel loyal to former president Ali Abdullah Saleh has been killed in clashes with rebels, Saleh's party said Sunday, in an unprecedented escalation of violence between the two allies.

Colonel Khaled al-Rida was killed in clashes in the rebel-held capital Sanaa late Saturday, a statement released by Saleh's General People's Congress party said. 

While the statement did not name the Huthi rebels, it accused a "group that knows no morality or oaths" of being behind the killing -- a thinly-veiled reference to the Huthis, who over the past week have lashed out at Saleh as a "back-stabber" and "traitor" as tensions rise within the rebel alliance.