The Japanese Olympic delegation expressed delight in having won a record 17 gold medals halfway through the Tokyo Games on Sunday, when it also criticized online abuse aimed at home Olympians from abroad.

Judo contributed a record nine golds, including two from the Abe siblings, Hifumi and Uta, while Yuto Horigome and 13-year-old Momiji Nishiya became the Olympics' first street skateboarding champions.

Japan's previous record was 16 golds, set at the 1964 Tokyo Games and equaled in Athens in 2004. Japan started the day with 30 total medals and looks to better its 41 from the 2016 Rio de Janeiro Olympics.

"Judo set us on our way...the new sports provided a breath of fresh air for Japan," deputy Chef de Mission Mitsugi Ogata said.

Japan won its first Olympic gold medals in table tennis, Jun Mizutani and Mima Ito winning mixed doubles, and fencing, in men's team epee. Daiki Hashimoto won his first men's individual all-around gymnastics title and Japan's third straight. Japan also defended the softball championship it won in 2008, before the sport was dropped from the Olympic program.

Badminton failed to produce a single gold despite high expectations, while Japan's three swimming golds, two by Yui Ohashi in women's individual medleys, were also fewer than expected.

"Getting to use facilities they are used to is definitely a home advantage. Feeling at home in having big support, although the games are held without spectators, is another," Ogata said.

"But it can work against some and I believe they suffered from the pressure of the Olympics."

The Japanese delegation, which originally set a target of 30 gold before the pandemic, asserted that the ultimate goal is winning the hearts of people through its performance amid the COVID-19-caused difficulties.

Hashimoto, Mizutani and men's surfing silver medalist Kanoa Igarashi, meanwhile, all revealed on social media that they have been the target of online abuse since winning their medals.

Chef de Mission Tsuyoshi Fukui condemned such acts as "insulting the athletes' years of efforts" and "simply intolerable."

"We are monitoring them (the accounts) and keeping records," he said, while senior Japanese Olympic Committee executive board member Keiko Momii said heinous cases will potentially be brought to police.