US prosecutors on Wednesday upgraded the charge against a former Minneapolis officer who pressed his knee into George Floyd's neck to second-degree murder, also charging three other former officers involved in the incident with aiding and abetting murder, reported Xinhua news agency.

Minnesota Attorney General Keith Ellison announced at a news conference that Derek Chauvin, the now fired and arrested Minneapolis Police Department officer who court documents said knelt on Floyd's neck for almost nine minutes, was charged with second-degree murder, an enhanced charge from the third-degree murder and manslaughter he was previously accused of.

"I believe the evidence available to us now supports the stronger charge of second-degree murder," Ellison said.

Additionally, the attorney general announced that arrest warrants were issued for three other officers who, also fired by the department, were involved in the death on May 25 of the 46-year-old black man.

Thomas Lane and J. Alexander Kueng, who helped Chauvin constrain Floyd, and Tou Thau, who stood by without stopping his colleagues, were charged with aiding and abetting murder, Ellison said. "I strongly believe that these developments are in the interests of justice for George Floyd, his family, our community and our state."

Informing reporters that he is the lead prosecutor of the case, Ellison acknowledged that although the prosecution team believe in the appropriateness of the charges they filed, "what I do not believe is that one successful prosecution can rectify the hurt and loss that so many people feel."

He added that "constructing justice and fairness in our society" would be a "slow and difficult work" ahead, urging leaders in government and all citizens "to begin rewriting the rules for a just society now."

In response to the just-announced charges, Benjamin Crump, the attorney for George Floyd's family, said it is not a time for celebration since an arrest is not a conviction, adding that the family wanted Chauvin to be charged with first-degree murder.

"We cannot celebrate because an arrest is not a conviction, and we want justice," Crump said. "You know, we don't want partial justice. We want whole justice." Crump said.

"The family has always wanted first-degree murder. They wanted him charged to the full extent of the law," he added, referring to Chauvin.

Further condemning racial injustice in the United States, the lawyer said "there are two justice systems in America. One for black America and one for white America, when there should be equal justice for the United States of America."

One of the ex-officers, J. Alexander Kueng, is set to appear in court Thursday afternoon, according to court records.

Asked about the timetable of the prosecution process, Ellison said "we're probably a number of months before this case will be in front of a jury."

--BERNAMA