Impacting the 2024 US presidential elections, Donald Trump will become the first former American President to go on trial following his indictment on charges relating to a payoff to buy the silence of an adult film star who claimed to have had an affair with him in 2016.

Manhattan prosecutor Alvin Bragg's office confirmed the indictment by a grand jury on Thursday evening and said Trump's lawyer has been contacted "to coordinate his surrender", which would be an unprecedented event in the history of the US.

While the indictment remained under seal, media reports quoting unnamed sources said that there were about 30 separate charges.

Complicating the scenario, Trump is a frontrunner for the 2024 elections, just 1 per cent behind President Joe Biden in polls, according to RealClear Politics which aggregates survey results.

He is also ahead of his nearest rival, Florida Governor Ron DeSantis, by 16.8 per cent for the Republican Party's nomination.

Under the US constitution, his indictment or even a conviction will not prevent him from running for President.

But were he to win in spite of an indictment or even a conviction, the US will be in unchartered territory.

Trump said the indictment "is political persecution and election interference at the highest level in history".

Indian-American member of the House of Representatives member Raja Krishnamoorti said in an email to supporters that "in moments like these, we are reminded that no one is above the law, not even former Presidents".

"We know Trump will use his indictment to rile up his supporters and raise millions for his next presidential bid," he added.

Trump is also facing two other probes -- one for his role in the January 6, 2016, riot by his supporters who stormed the Capitol that houses Congress, and the second for alleged attempts to interfere with the 2020 election results in Georgia.

According to one of his lawyers, Susan Necheles, Trump would turn himself in to authorities on April 4.

In what would be an unprecedented scene, as a former president, Trump is under Secret Service protection and the federal agency would be coordinating the arrest with New City officials and protecting him.

If the usual procedures are followed, he would be fingerprinted, photographed and handcuffed and produced before a judge who would decide whether to keep him in custody or release him.

Often in a ritual known as "perp walk", the accused "perpetrator" would be paraded in handcuffs before news cameras and Trump may want it to portray himself as a martyr and rile up his base.

According to media reports, Trump has discussed being handcuffed and considered if the sight would rally his supporters.

The grand jury proceedings are secret and while the exact charges will not be known till the indictment is made public, he was facing allegations that he falsified the business records about the $130,000 paid to adult film star Stormy Daniels who claimed to have had an affair with him, and that he violated elections laws through the payoff to buy her silence.

The affair, which he has denied, and the hush money payment are not themselves illegal, and the prosecutors will have to prove that the payments shown as lawyer's fees paid to his former lawyer Michael Cohen who in turn passed on the money to Daniels violated laws on bookkeeping.

While that would be a misdemeanour or minor offence, connecting the payments to violations of election finance laws would make it a felony or major crime with a prison sentence that could be of several years.

Cohen was convicted in a federal court of election law violations for making the payments to Daniels and $125,000 to another woman and sentenced to three years in prison.

Federal prosecutors and Bragg's predecessor Cyrus Vance considered bringing a case against Trump, but dropped the idea.

Daniels asserted that the affair took place in 2006 when Melania Trump had a baby.

The hush money was paid ten years later on the eve of the 2016 presidential election when Daniels was trying to air it.

Under the New York legal system, prosecutors have to convene a grand jury made up of 16 to 23 ordinary citizens who will consider preliminary evidence in secret sessions and vote on an indictment -- that there is a prima facie case to frame charges.

When the charges are filed and a trial is held, a jury of 12 citizens will decide the case with a unanimous decision required for a conviction, unless the accused agrees to the judge giving the verdict without a jury.

Trump had warned in a social media post over the weekend of "death and destruction" if he was indicted and police were put on alert in New York City and elsewhere if his supporters would respond to his calls for protests.

Officials fear a repeat of the January 6, 2021, riot by his supporters to prevent Congress from ratifying his election which endangered members of Congress and Vice President Mike Pence.

There was no noticeable protest in New York City on Thursday, while a group collected outside his current home in Mar-a-Lago estate in Florida where he is staying in a show of support.

Biden has remained silent on the Trump case to avoid the impression of electoral meddling.

The leader of the majority Democratic Party in the Senate, Chuck Schumer, called on Trump and his supporters to act peacefully and said that he "is subject to the same laws as every American".

He will be able to avail himself of the legal system and a jury, not politics, to determine his fate according to the facts and the law."

Most Republican leaders have rallied to support Trump, who has a strong base in the party, despite any reservations they may have.

House Speaker Kevin McCarthy asserted that the indictment "irreparably damaged our country in an attempt to interfere in our Presidential election" and vowed to carry out a Congressional investigation of Bragg.

DeSantis tweeted: "The weaponisation of the legal system to advance a political agenda turns the rule of law on its head. It is un-American."

He said that Bragg is "backed" by George Soros, the multi-billionaire who backs progressives in the Democratic Party while trying to meddle in the internal affairs of other countries, including India.

Prosecutors in New York are elected in partisan elections and Bragg was the Democratic Party candidate, who was backed by a Soros-financed organisation that spent $500,000 to back his campaign.

As President, Trump was impeached twice by the House of Representatives when it was under Democratic control, first on misusing his position to get Ukraine to implicit Biden's son in questionable financial deals and second regarding his role in the Capitol riot.

Both times he was acquitted by the Senate which had Republican majority at that time.

This time his fate will rest with a local court in New York City, where he was born and built his real estate empire and his showbiz persona till he moved to Washington as president.

The riot by Trump's supporters who fought their way into the Congress premises endangering lawmakers brings the spectre of violence over his calls for protests over his indictment.

The exact charges were not immediately known as the grand jury hearings and its vote are secret.

Neither the alleged affair nor the payments are of themselves illegal and the potential charges he faces are falsifying business records for allegedly hiding the payments as lawyer's fees and illegally using the payments to further his election.

Under New York legal procedures, a grand jury -- a panel made up of citizens -- holds a secret preliminary hearing on allegations to determine whether there is a prima facie case to bring charges for trial.