Yes, precisely, the hot, flaming air in a gas turbine is decelerated (negative acceleration) by the blades, and in the process the air is both slowed and cooled. The blades then react (newton's opposing force) and produce the opposite force which is then reacted (eventually) against the rotor. The rotor smacks the outside air and accelerates it, causing the lift force.
For a pure turbojet, the burning fuel causes a temperature rise in the gas, which pushes against the combustion chamber (which is why rockets and jets have strong steel housings - to withstand and react the force against them), the chamber reacts this pressure force, and this reaction presses the hot gas out the open back end. The pressure is a force that accelerates the hot air.