Reina sits stunned after the final whistle.
Liverpool manager Rafael Benitez was critical of Austrian referee Konrad Plautz for the amount of added time he played, but had sympathy for Norwegian defender Riise.
"These situations are difficult. You can't blame the player. Those kind of balls when they bounce are difficult to deal with," he told reporters.
"We are all very disappointed to concede an own goal so late in the match. But we had three clear chances and in games like these it is hard to create chances. We created chances and we needed to take them.
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