Having upset the odds to beat seeded player Mansoor Zaman Jnr of Pakistan yesterday, the unranked 17-year-old from Bogotá needed 54 minutes to see off the world number 482 with a 10-12, 11-9, 11-6, 6-11, 11-9 victory.

"I was two-nil 10-7 down yesterday, and today I was 10-7 up in the third and it was very hard to finish," Knudsen, who is coached by former world number 38 Martin Knight of New Zealand, said.

"I'm so excited to be in the last-16.

"This is my third world juniors.

"I'm getting further each time and I still have one more to go."

Bidding to become Colombia’s first-ever quarter-finalist at the event, Knudsen now faces number two seed Mohammad Al Sarraj of Jordan.

Al Sarraj defeated the United States’ Salim Khan 11-7, 11-9, 12-10.

There was a further upset in the men's draw as unseeded Egyptian Aly Hussein, a World Championship debutant, defeated seeded player Roman Allinckx of Switzerland 11-6, 11-4, 11-5.

The 17-year-old, one of five Egyptians through to the men's last-16, will have to overcome India's Adhitya Raghavan to secure a place in the quarter-finals.

Raghavan beat South Korea's In Woo Lee 11-5, 11-6, 4-11, 11-9.

Egypt’s Jana Shiha produced the stand-out result of the day in the women's event after ousting seeded player Akanksha Salunkhe of India.

Shiha's 11-6, 11-8, 11-4 win in just 16 minutes takes her through to the last-16 where she will face compatriot Rowan Reda Araby.

Araby, last year's runner-up, overcame Canada’s Nicole Kendall 11-1, 11-2, 11-2.

Top seed Hania El Hammamy of Egypt brushed aside Hong Kong's Ka Wing Ho 11-4, 11-3, 11-2.

El Hammamy was one of six players from her country to reach the fourth round.

Another was predicted semi-finalist Nada Abbas, who came from behind to beat India's Aishwarya Bhattacharya 11-4, 8-11, 9-11, 11-6, 11-3.

Home favourite Kaitlyn Watts, the highest-ranked New Zealander in the women's draw, was unable to pull off the upset she needed to reach the fourth round after falling to a 4-11, 7-11, 4-11 defeat against Malaysia’s Chan Yiwen.