* Officers found not guilty of killing protesters in 2011
* Opposition walks out of parliament over acquittal
* U.S. embassy says "dismayed" by ruling
By Benet Koleka
TIRANA, Feb 7 (Reuters) - An Albanian court on Thursday found two state guards not guilty of killing four people during an anti-government protest in 2011 - a ruling that dismayed opposition politicians and Albania's ally the United States.
Members of the main opposition Socialist party stormed out of parliament in protest at a verdict they said showed those in power could get away with murder.
Four protesters were killed on Jan. 21, 2011 after shots were fired from inside the compound of the prime minister's building, as a protest against government corruption and election fraud outside the walls turned violent.
The prosecution was seeking sentences of 23 and 25 years for the two Republican Guards, whose job it is to protect government buildings and high-level officials. The defence said they had fired warning shots but that the bullets had been deflected.
The deaths deepened a rift between government and opposition and halted reforms needed to take Albania closer to the European Union membership.
"On behalf of the bereaved families, I want to remind (the defendants) that neither of them will escape justice. We have nothing to do in this parliament," Socialist lawmaker Saimir Tahiri told parliament before walking out.
The United States, which provided assistance to the investigation, said it was "dismayed" by the ruling.
"Regrettably, today's verdict has undermined confidence in the ability and willingness of the Albanian judicial system to deliver justice in an impartial, transparent manner," the U.S. embassy said in a statement.
The prosecution will decide later whether to appeal. (Reporting By Benet Koleka; Editing by Zoran Radosavljevic and Robin Pomeroy)