Real Madrid survived a real scare to qualify for their fifth successive Champions League quarter-final despite conceding four away goals to an impressive Schalke.

The holders were hanging on in the final few seconds as Schalke were just one goal away from producing one of the competition's biggest shocks after winning the second leg.

Trailing 2-0 after the first leg, Schalke twice led - through Christian Fuchs and ex-Real striker Klaas-Jan Huntelaar - but Cristiano Ronaldo levelled each time with a header.

Karim Benzema gave the hosts the advantage on the night after the break but goals from Leroy Sane and Huntelaar saw a below-par Real endure a nervous finale in a thrilling encounter.

World Player of the Year Ronaldo became the Champions League's record scorer but, for once, the Portuguese was not the story as Bundesliga side Schalke threatened what was almost the unthinkable.

Only Barcelona and Juventus have won by a two-goal margin in the Champions League at the Bernabeu in the last 10 years but Schalke were only denied just that by desperate late defending.

Los Blancos ended a 12-year wait to capture 'La Decima' - a 10th European Cup win - last season, having beaten Schalke 9-2 on aggregate at the same stage of the competition.

But, despite fifth-placed Schalke being 23 points behind Bundesliga leaders Bayern Munich, there was no sign of a repeat as they finished with a 4-3 second-leg win, a scoreline with 500-1 odds before kick-off.

Real boss Carlo Ancelotti has been criticised by some supporters after four defeats since the turn of the year and losing La Liga top spot to Barcelona.

And the hosts' recent frailties were being exposed by a slick-passing Schalke, who took a deserved lead when Fuchs fired home from inside the penalty area, after a dummy by Huntelaar.

Ronaldo's headed leveller should have eased Real's nerves but the shock was still on as Schalke refused to let their hosts take any sort of control and regained the lead on the night through Huntelaar's close-range finish.

Knowing one more goal without reply would see them qualify, Schalke were dealt a harsh blow just before the break as Ronaldo again headed the defending champions level.

His two headers take his Champions League tally to 76 goals, one ahead of Barcelona's Lionel Messi, who plays in the last 16 against Manchester City next week.

He has also scored 60 goals in his last 59 Champions League appearances and 41 goals in all competitions this season. In contrast under-pressure Gareth Bale again had a quiet evening.

Benzema then finished smartly from inside the area after a weaving run but Schalke refused to go away quietly as 19-year-old substitute Sane curled into the net from 20 yards to level the scores on the night again.

An already tense evening became even more dramatic as Huntelaar's powerful 18-yard shot gave Schalke victory on the night and left the dismal hosts having to survive a frantic finale to limp through.