(REUTERS) - Ultimate Fighting Championship (UFC) middleweight champion Israel Adesanya has apologised after he said on social media that he would "rape" fellow fighter Kevin Holland.

Nigerian-born Adesanya posted an expletive-laden video on Instagram earlier this week directed at Holland, who had targeted him in a series of remarks.

The 31-year-old, who currently resides in New Zealand, later deleted the video and said he had "crossed the line".

"I understand the gravity of this word and how it can affect and hurt other people apart from my opponent, although that was never my intention," he tweeted.

"I am still growing under the spotlight, and I take this as a lesson to be more selective with words under pressure."

His apology came after Grant Robertson, New Zealand's Deputy Prime Minister and Minister of Sport and Recreation, condemned his comment.

"We have to take rape seriously. It's not an issue that anyone should be making jokes or flippant comments about at all," Mr Robertson said.

Adesanya was undefeated in mixed martial arts with a 20-0 record until he was beaten by Jan Blachowicz in a light heavyweight title match at UFC 259 on March 6.