(Reuters) - German Tony Martin claimed a record-equalling fourth individual time trial world title when he crushed his rivals to prevail on the 40-km flat course in Doha on Wednesday.

Martin, who was instrumental in Etixx-Quick Step's team time trial title last Sunday, clocked 44 minutes 42.99 to beat defending champion Vasil Kiryienka, of Belarus, by 45.05 seconds.

Spain's Jonathan Castroviejo finished third, 1:10.91 off the pace in searing heat as temperatures rose above 40 Celsius.

Martin joins Swiss Fabian Cancellara, who retired after winning the event at the Olympics in Rio, at the top of the list of winners.

Cancellara won his four titles in 2006, 2007, 2009 and 2010 while Martin, who is leaving Etixx-Quick Step to join Katusha next season, had won three times in a row from 2011.

Having also won one silver and two bronze medals in the event, Martin surpassed Cancellara, who also won three bronzes, as the most successful time trialist.

Several pre-race favorites disappointed, with Dutchman Tom Dumoulin, regarded in the buildup as Martin's main rival, finishing 11th and Australian Rohan Dennis taking sixth place.

"After taking the gold medal with the team, to win the rainbow jersey in the individual time trial is just the icing on the cake," said Martin.

"I was a bit scared by the heat at first, but having a good preparation here in Qatar helped me cope with it. I rode without any pressure, was focused only on what I had to do, and not on my rivals, and to come out on top is really incredible.

"I haven't had a great year up until this point, but to win two world titles in the space of just four days makes up for everything."

(Reporting by Julien Pretot; Editing by Neville Dalton and Toby Davis)