Rio 2016 Olympics: Day 4 as it happened

(CNN) Day four at Rio 2016 was another golden bonanza for swimming superstar Michael Phelps, who added two more titles to his record career tally.

Hungary's "Iron Lady" Katinka Hosszu continued her fine form in the pool, notching her third gold medal, while American Katy Ledecky bagged her second of the Games.

Tuesday's headlines:

• Michael Phelps wins 21st gold (11.53 p.m.); Diving pool turns green (5.37 p.m.)
• Tennis shocks continue as Serena Williams exits (8.06 p.m.)
• US women retain all-round gymnastics title (6.20 p.m.)
• NZ rugby superstar ruled out after shock loss to Japan (2.38 p.m.)

Recap all the action below and go here for our full Rio 2016 coverage.