Uganda's Joshua Cheptegei, American Ryan Crouser (shot put), German Johannes Vetter (javelin) and Norwegian Karsten Warholm (400m hurdles) were the other male finalists at the virtual ceremony.
They were put in isolation after American pole vaulter Sam Kendricks tested positive for COVID-19.
The Italian and Japanese battled shoulder-to-shoulder as the leading pair in the final 4km, but the Italian coped well with the pressure and accelerated in the final 300m to seal the gold medal.
Jamaica's Elaine Thompson-Herah made Olympic history in Tokyo Tuesday, blazing to victory in the 200 metres to complete an unprecedented women's sprinting "double-double".
Compatriot Ronnie Baker, who had set the previous fastest 100m of the year nine days ago, was second in 9.93 seconds, with Jamaica's Yohan Blake third a further hundredth of a second back.
A summary of sports events and persons who made news on Monday
alaika Mihambo of Germany snatched the Olympic gold in women's long jump with her final leap of 7.00 metres in an enthralling final at the Tokyo Games on Tuesday.
American Noah Lyles shot to 200 meters world championships gold on Tuesday, providing a bright finish to a day darkened by yet another doping scandal.
A summary of sports events and persons who made news on Saturday