Unbeaten Belgium have 21 points from seven games, with only one goal conceded, with Russia on 18 and Cyprus, 2-1 winners over Kazakhstan in Astana, on 10. The top two in each group qualify directly.
San Marino managed to keep a clean sheet for 27 minutes against the top-ranked 2018 World Cup semi-finalists before, as expected, the Group I floodgates opened at Brussels’s King Baudouin stadium.
Inter Milan striker Lukaku became the first Belgian to reach a half century of international goals with a right-footed shot to open the scoring.
He then set up Nacer Chadli three minutes later before an own-goal from Cristian Brolli put Belgium 3-0 up in the 35th. Lukaku then grabbed his second on 41 minutes assisted by Real Madrid’s Eden Hazard.
A deflected Toby Alderweireld effort in the 43rd minute and a Youri Tielemens shot in stoppage time saw Belgium cruise in 6-0 up at the break.
The pace slowed before Christian Benteke scored in the 79th, three minutes after coming on, wrong-footing the goalkeeper from the edge of the area.
Yari Verschaeren made it 8-0 from the penalty spot in the 84th and Timothy Castagne rounded off the tally in the 90th minute.
Russia dominated possession at the Luzhniki stadium but were frustrated throughout the first half by a Scotland side that failed to muster a single shot on target.
The Scots, who can no longer qualify automatically but remain in contention through the playoffs, crumbled after the break.
Artem Dzyuba made the breakthrough for Russia on the volley in the 57th and a second followed three minutes later when Magomed Ozdoev blasted a long-range screamer past David Marshall.
Dzyuba headed in his second in the 70th minute, with an Aleksandr Golovin shot going in off the post in the 84th, as Russia cruised to a comfortable win.
Memphis Depay scored twice and Luuk de Jong was also on target as the Netherlands came back from a goal down with 10 minutes left to beat Northern Ireland 3-1.
It was a fortunate escape for the home side who fell behind when Josh Magennis gave Northern Ireland the lead in the 75th minute after a stout defensive performance had frustrated the hosts.
Yet the Dutch responded with an equaliser from Depay in the 80th minute and then two stoppage-time goals that put them in a three-way tie at the top of Group C.