An open letter written on behalf of Ukrainian athletes to International Olympic Committee (IOC) President Thomas Bach and International Paralympic Committee (IPC) President Andrew Parsons has urged them to take action following Russia's invasion of Ukraine.

The letter, since published by Global Athlete, received 40 signatories representing several of the country's National Federations and has also garnered support from non-Ukrainians.

This includes fencer Sofiya Velikaya, a two-time Olympic champion and chair of the ROC Athletes' Commission, according to Global Athlete.

Velikaya was re-elected in December 2021, and offered support in a personal capacity.

The NOC of Ukraine Athlete Commission supports the letter, with Olga Saladukha signing on its behalf.

"Dear Mr Bach, dear Mr Parsons, we write to you today on behalf of Ukrainian Athletes to call on you in your leadership capacity of the International Olympic Committee and International Paralympic Committee to immediately suspend the Russian and Belarusian National Olympic and Paralympic Committees," the letter reads.

"Russia's invasion of Ukraine, supported by Belarus, is a clear breach of the Olympic and Paralympic Charters - a breach that must be met with strong sanctions."

Canada's four-time Olympic ice hockey gold medallist Hayley Wickenheiser, a former IOC Athletes' Commission member, has also given the letter her support.

Wickenheiser was joined by Canadian rowers rowers Andrea Proske, who won gold in the Tokyo 2020 women's eight, and Jennifer Casson.

"If the IOC and IPC refuse to take swift action you are clearly emboldening both Russia and Belarus' violation of international law and your own charters," the letter continued.

"Your lack of action will send a message to every athlete and the world that you have chosen Russia and Belarus' interests over athlete interests.

"Your legacy will be defined by your actions."

IOC Athletes' Commission chair Emma Terho and her IPC equivalent Jitske Visser have also been copied into the letter, which is supported by Ukrainian bobsleigh and skelton, luge, swimming, gymnastics, athletics and biathlon athletes.

As the Russian invasion enters its fifth day, the United Nations has confirmed that there have been 376 civilian casualties in Ukraine including 94 deaths.

More than 210 Ukrainians have been killed according to Ukrainian Parliament Commissioner for Human Rights Liudmyla Denisova.

The Ukrainian President Volodymyr Zelenskyy has claimed that 4,500 Russian soldiers have been killed since the attack began.