Republican presidential candidate Donald Trump is stepping up his attacks on Vice President Kamala Harris following the Democratic National Convention.

Trump held a rally in Arizona on Friday, filling a 19,000-seat indoor facility despite scorching outdoor temperatures of about 40 degrees Celsius. Reports say more than 100 people were treated for suspected heatstroke.

The former President spoke about the Democratic convention that ended in Chicago the previous day. Key Democratic figures, including Harris and ex-President Barack Obama, delivered speeches.

Trump said, "Last night, Kamala mentioned my name 21 times." He added that she did not say anything but his name repeatedly, instead of talking about border control and economic measures.

Trump argued that his advisors are telling him to stick to policy rather than talking about personalities, even though Harris kept bringing his name up.

At the event, Trump also welcomed Robert F. Kennedy Jr., an independent presidential candidate who suspended his campaign and endorsed Trump. His appearance onstage drew especially loud cheers.

Trump is holding rallies every day, focusing on battleground states while media attention has been on the Democratic convention.