Republican presidential nominee Donald Trump on Friday afternoon defended his late-night tweeting, casting his tendency to be awake in the middle of the night as a virtue rather than a concern.

Trump unleashed a string of tweets starting at 3 a.m. on Friday, blasting the media and attacking former Miss Universe Alicia Machado, who has spoken out against him.

"For those few people knocking me for tweeting at three o'clock in the morning, at least you know I will be there, awake, to answer the call!" he tweeted Friday afternoon.

Here are the tweets in question: