The hosts had the lion’s share of possession but Iceland repeatedly showed themselves to be dangerous on the counter and could have gone into halftime ahead were it not for a couple of decent saves from Belgium’s Thibaut Courtois.
Belgium’s 11th minute opener came directly from the training ground as Nicolas Lombaerts charged forward and deftly headed Adnan Januzaj’s free kick into the net.
But the hosts, missing injured captain and central defender Vincent Kompany, held on for little more than a minute before Iceland’s Alfred Finnbogason found himself unmarked at the back post from a corner for an easy tap-in
Substitute Origi re-established Belgium’s lead in the 62nd minute, feigning right, then cutting inside to blast home with his left beyond Iceland’s Ingvar Jonsson.
Shortly afterwards, Club Bruges’ Thomas Meunier opened up Iceland’s defence, before passing to Dries Mertens who fed Lukaku in front of an open net to settle the encounter.
Iceland had won their three opening Euro 2016 qualifiers, including a 2-0 victory over the Netherlands a month ago, to top group A on goal difference from the Czech Republic, who they visit on Sunday.
Belgium will on the same day host Group B leaders Wales, the last side to beat Iceland, in a friendly in March.
Belgium will be heartened by the fine form of Courtois and the return of Christian Benteke, playing his first match since March.
The striker, currently serving a three-match Premier League ban, delivered what Belgium have lacked in his absence, a man to hold the ball up front.
(Reporting By Philip Blenkinsop)