After a dramatic six-hour-long standoff with security, South Korean police have called off an attempt to arrest suspended President Yoon Suk Yeol.

The military and Yoon's security service officers formed a human wall and used vehicles to block the arrest team's path, local news outlet Yonhap reported.

Yoon is under investigation for abusing his power and inciting an insurrection when he tried to impose martial law in early December.

The move, although short-lived, led to a political crisis as Yoon was impeached by an opposition-led parliament and suspended from office.

A Seoul court issued a warrant for his arrest early this week after he ignored three summonses for him to appear for questioning.

If they had been successful, Yoon would have become the first sitting president to be arrested in South Korea's history.

Since early morning on Friday, dozens of police vans lined the street outside Yoon's residence in central Seoul.

At about 08:00 local time (23:00 GMT), an arrest team made up of police officers and CIO members marched towards the compound.

The operation started out with a 20-strong team, but quickly multiplied to some 150 people. Even then, they were outnumbered.

While about half of the team was able to get inside, they were locked for hours in a standoff with security officers - who are still responsible for protecting Yoon, despite him being stripped of his powers - and a military unit responsible for protecting the city of Seoul.

At one point Yoon's security team engaged in a "confrontation" with the investigating officers, an official with Seoul's Joint Chiefs of Staff told AFP.

"We've determined that the arrest is practically impossible," said the Corruption Investigation Office (CIO), which has been investigating Yoon's short-lived martial law declaration last month.

Yoon's "refusal of the legal process" is "deeply regrettable", the CIO said, adding that next steps will be decided after a review.

Yoon's supporters, who have been camped out in front of the presidential residence for days, cheered in song and dance as the suspension was announced. "We won!" they chanted.

The CIO said that concern for the safety of the team on the ground was another factor in their decision to call off the attempted arrest.

What's next?

This development is not unexpected, given Yoon's defiance throughout the investigation process.

Experts say that as a former chief prosecutor, Yoon is well aware of the legal loopholes available for his defence.

Investigators have until 6 January to arrest him before the current warrant expires.

This means they may attempt to arrest Yoon again over the weekend, although this could be logistically challenging as the crowds are likely to swell.

They can also apply for a new warrant and try to detain him again.

Before the attempt was stood down, Yoon's security team told the news agency they had been "in negotiation" with the investigators who sought to access the president.

Police have opened a criminal case against the chief of Yoon's security service and his deputy, and summoned them for questioning, according to Yonhap.

Yoon's legal team was also seen entering the residence slightly past noon local time.

His lawyer Yoon Gab-keun earlier said they would take legal action over the arrest warrant, arguing that investigators lacked the authority to detain him.

Meanwhile, Park Chan-dae, the floor leader of the main opposition Democratic Party, has criticised Yoon for not upholding his promise to take legal and political responsibility for his botched martial law attempt.

"[It was] a complete lie," Park said, urging the CIO to attempt to arrest Yoon again today.

The CIO, which has only been operating for four years, was created in response to public anger over former president Park Geun-hye and her excesses. She was impeached by parliament in December 2016, and removed from office three months after.

The extent of the CIO's jurisdiction, however, has been challenged by other agencies - and its failure to deal with Yoon could be seen as an embarrassing loss.

Weeks of chaos

South Korea has been in political chaos since the martial law attempt on 3 Dec, with wide rifts opening in parliament between Yoon loyalists and those seeking to unseat him.

Days and nights of protest culminated in the opposition-dominated parliament voting to impeach Yoon on 14 December, their second attempt to do so after the majority of his ruling party members boycotted the first vote.

Two weeks later, parliament voted to impeach his replacement, acting president Han Duck-soo - the first time an acting president had been impeached since South Korea became a democracy.

Han was supposed to lead the country out of its political turmoil, but opposition MPs argued that he was refusing demands to complete Yoon's impeachment process.

On Friday, prosecutors also indicted on insurrection charges army chief Park An-su, who was named martial law commander during the brief declaration, and special forces commander Kwak Jong-geun, according to Seoul-based news outlet Yonhap.

They are to face trial while in prison.