BAGHDAD (AP) — The al-Qaida breakaway group that has seized much of Syria and Iraq has formally declared the establishment of a new Islamic state, demanding allegiance from Muslims worldwide in a move that could further strain relations with other militant groups.

With brutal efficiency, the Sunni extremist group has carved out a large chunk of territory that has effectively erased the border between Iraq and Syria and laid the foundations of its proto-state. But Sunday’s declaration, made on the first day of the Muslim holy month of Ramadan, could trigger a wave of infighting among the Sunni militant factions that formed a loose alliance in the blitz across Iraq.