Wall of flames - Great Fireball Technique

“Water Style!” Kiruru shouted, and that’s as far as they got.
The wall of flames that abruptly materialized before them scared the three
senseless, to the point where they actually forgot to activate their own
techniques.

At a speed three times that at which the three were weaving signs, Itachi
had activated the Fire Style: Great Fireball Technique. He used chakra that he
had been building up the whole time, during the first exam, and from the start
of the second exam. The field of view of the opposing team should have been
swallowed up by flames in an instant. He had released these flames with such
control, that they were at a distance that was just barely not a direct attack on
the three. The flames were meant only to be threatening.

This was a test. There was no need to kill or injure anyone. All he needed
was for his opponents to lose heart.
The flames danced up to the heavens, and disappeared.
Legs trembling, almost giving out from under them from fear, the three
still managed to stay on their feet somehow. A thin veil of tears welled up in
the eyes that stared at Itachi.

Book of Bright Light Chapter 3 Part 1