BUDAPEST—American Hunter Armstrong won gold in the men's 50m backstroke in a dramatic finish at the world championships in Budapest on Saturday after compatriot Justin Ress was disqualified despite touching the wall first for being fully submerged at the finish.
Ress had set the pace in the heats and the semi-finals and looked set for gold until officials ruled that no part of his body was above the water as he reached for the wall.
Polish teenager Ksawery Masiuk took silver while Italy's Thomas Ceccon, who set a new world record in the 100m backstroke earlier in the competition, claimed bronze.
Canadian Summer McIntosh continued her superb run in the Hungarian capital after the 15-year-old beat fellow teen Katie Grimes of the United States to collect the 400m medley title. U.S. swimmer Emma Weyant came a distant third.
Gregorio Paltrinieri, the gold medallist at the Rio Olympics, set a new championship record in the 1,500m freestyle, comfortably finishing ahead of Robert Finke and Florian Wellbrock in a time of 14:32.80.
The Italian looked on course to break Sun Yang's world record of 14:31.02 but faded in the last 100 meters.
Swede Sarah Sjostrom added the 50m freestyle crown to her remarkable list of victories as she claimed a 19th individual medal at the world championships, edging out Katarzyna Wasick and Meg Harris.
Earlier, former Olympic champion Ruta Meilutyte clinched gold in the women's 50m breaststroke, beating Italian Benedetta Pilato by 0.10 seconds, with Lara van Niekerk of South Africa coming home in third.
Lithuanian Meilutyte was handed a 24-month suspension in 2019 for anti-doping violations and returned to competitive action only in December last year.