Katie Ledecky made history on Tuesday by becoming the first woman to win 12 world swimming championship gold medals, as world records were sent tumbling four times in the Budapest pool.

Britain's Adam Peaty twice lowered his own men's 50m breaststroke record, once in the morning's heats then again in the evening's semi-finals.

Canadian Kylie Masse then broke the women's 100m backstroke record from 2009, when now-banned neoprene suits were used.

To complete the drama, Lilly King of the United States took out the women's 100m breaststroke world record to take the gold.

"It was not really on my radar to swim below 26 seconds but I felt good tonight," said Peaty who swam 26.10 secs in the morning, then 25.95 in the semi-final.

"Let's see what comes out in tomorrow's (Wednesday's) final."

Ledecky proved she is peerless in the women's 1500m freestyle as she won the final by a massive 19.07 seconds ahead of her nearest rival, Spain's Mireia Belmonte.

- 'Another planet' -

"Katie Ledecky is on another planet, so the goal of the race was to win the silver medal. For me, it is gold," quipped Belmonte.

Ledecky, 20, is now the most decorated woman in world swimming championships history as she passed compatriot Missy Franklin, who has 11 world titles.

But despite her achievement, Ledecky said winning is not as easy as she makes it look.

"It's hard the other 364 days of the year, it's about putting the work in during practice, so that then I can step up," she said.

King, also 20, claimed the United States' second gold of the night with a commanding display in the women's 100m breaststroke final.

She clocked one minute 04.13 seconds in the final, beating Ruta Meilutyte's 2013 record, to add world gold to the Olympic title she won last year in Rio de Janeiro.

Masse, 21, then proved the current depth in women's backstroke with a devastating display.

The 21-year-old clocked 58.10 seconds, breaking Gemma Spofforth's previous mark of 58.12sec from the 2009 championships.

"I was making sure I was reading the right name and the right time I was lost for words immediately after, I'm still in shock," said a stunned Masse.

Kathleen Baker of the United States took silver, at 0.48sec back, while Emily Seebohm of Australia brushed off a cold to claim bronze, just 0.49 behind.

- 'Awesome record' -

"It's awesome, I kinda thought she would do it," said Seebohm, the 2015 world champion, of Masse's record.

"I didn't come in saying 'I'm going to defend my title', but to rather enjoy racing these girls, they're fantastic, there's great depth in the backstroke."

Earlier, Chinese superstar Sun Yang won the men's 200m freestyle gold to add to his Olympic title in the same event.

Sun touched the wall first in one minute 44.39 seconds to set a new Asian record.

"It was a great race, especially the last 50 metres were pretty good. It is one of the hardest races for me," said Sun, who punched the water in triumph after his victory.

It was Sun's second gold of these championships after his victory in the 400m freestyle final on Sunday.

He will bid for the treble in Wednesday's 800m free –- the event he has dominated for the last three world championships since 2011 in Shanghai.

Xu Jiayu claimed a second gold for the night for China by winning the men's 100m backstroke final.

The 21-year-old Olympic silver medallist clocked 52.44 seconds with American duo Matt Grevers earning silver, at 0.04sec back, and Olympic champion Ryan Murphy taking bronze at 0.15

Source: AFP