Ahmed Musa scored both goals as Nigeria swept aside World Cup debutants Iceland to leave Group D intriguingly poised with one round of games to go.
The Super Eagles would have gone out with defeat but came good in Volgograd.
Musa showed superb technique to fire Nigeria ahead on the half-volley before the Leicester player rounded keeper Hannes Thor Halldorsson to make it 2-0.
Iceland missed a late penalty awarded after a video assistant referee review, Gylfi Sigurdsson firing over.
The result gives a slight lift to beleaguered group rivals Argentina. Victory over Nigeria in their final game would see La Albiceleste safely into the last 16 – as long as Iceland do not beat group leaders Croatia. In that event, goal difference would decide who progressed.
Victory in that game for Nigeria, on the other hand, would now guarantee their progress. Having started the day bottom of the group, they find themselves second – three points behind Croatia, who have already qualified for the knockout stage.
Iceland, who face Croatia on Tuesday, and Argentina, who play Nigeria at the same time, both have one point.
Having gone down 2-0 to Croatia in their first game, Nigeria would have joined African rivals Egypt and Morocco in exiting the tournament early if they had lost here.
They started slowly, becoming the first team in Russia not to have a shot in the first 45 minutes.
Yet they were a different proposition after the interval as they went on to secure only a second win in 14 games at a World Cup finals.
Musa, who ended last season at CSKA Moscow on loan from Leicester City, proved the difference having been recalled to the team after the Croatia defeat.
He showed exceptional quality to open the scoring, controlling a cross by Victor Moses before lashing home from 10-yards.
Having scored one of the goals of the tournament, Musa then hit the bar before scoring his second after Iceland’s defence had gone walkabout.
Nigeria still have to beat Argentina to make sure of extending their stay in Russia but this performance, particularly in the second half, will give them a huge lift for Tuesday’s group finale.