The Boston Celtics have suspended coach Ime Udoka for the 2022-23 season, effective immediately, and with no guarantee he will be back with the franchise in the future.

The Celtics said Udoka was suspended for "violations of team policies".

Earlier, two people with knowledge of the matter said Udoka was being sanctioned because of an improper relationship with a member of the organisation.

Those people spoke to The Associated Press on condition of anonymity because the team did not reveal that detail publicly.

"A decision about his future with the Celtics beyond this season will be made at a later date," the Celtics said.

Udoka, in a statement published by ESPN, apologised but did not offer detail.

"I want to apologise to our players, fans, the entire Celtics organisation, and my family for letting them down. I am sorry for putting the team in this difficult situation, and I accept the team's decision. Out of respect for everyone involved, I will have no further comment," he said.

One of the people who spoke to AP said Celtics assistant coach Joe Mazzulla would take over on an interim basis.

It's the second major disciplinary situation in as many weeks in the NBA, following the decision last week by commissioner Adam Silver to suspend Robert Sarver — the owner of the Phoenix Suns and WNBA's Phoenix Mercury — for one year and fine him $US10 million after an investigation showed his pattern of disturbing workplace conduct, including abusive and racist language. 

Sarver said on Wednesday that he intended to sell his teams.

AP