SLOVYANSK, Ukraine (AP) — The well-armed, Moscow-backed insurgency sowing chaos in eastern Ukraine scored a new victory Wednesday, seizing armored vehicles and weapons from underequipped government forces, then rolling through two cities to a hero’s welcome.

Responding to what it sees as Russia’s aggression, NATO announced it was increasing its military presence along its eastern border, closest to Russia and Ukraine. And the Obama administration moved to ratchet up its response, preparing new sanctions on Russia and boosted assistance for the struggling Ukrainian military.