- Denmark progress to Russia 2018
- Christian Eriksen scored a hat-trick
- Thirty of 32 World Cup spots have now been decided
Despite falling behind to a Shane Duffy strike after only six minutes, Denmark regrouped and made light work of the hosts, scoring five unanswered goals to book a place at next year's tournament in Russia.
The Republic had held the Scandinavian team goalless during the first leg, but it was not to be for coach Martin O'Neill's team, who had no response to an Andreas Christensen strike midway through the first half, which was swiftly followed by Eriksen's first.
The Tottenham Hotspur star then went on to score another two in the uneven contest, before Denmark striker Nicklas Bendtner wrapped things up with a late penalty.
Two places up for grabs
In Sydney, Australia beat Honduras 3-1 at Stadium Australia to qualify for their fourth successive World Cup.
The teams had played out a goalless draw in San Pedro Sula, but a hat-trick by Mile Jedinak -- two of which were from the penalty spot -- ensured the Socceroos progressed.
Only one World Cup place remains, which will be decided when Peru host New Zealand on Wednesday.
The first leg of that Oceania-CONCACAF playoff ended 0-0 in Wellington.
Victory over the Kiwis would see Peru in the World Cup finals for the first time since 1982.
Monday night saw one of the shocks of the qualifying rounds, with four-time champions Italy eliminated by Sweden