An International Criminal Court prosecutor has told judges that former Philippines president Rodrigo Duterte personally instructed members of a death squad to kill suspected criminals and drug users.
A court in The Hague is holding pre-trial hearings into three counts of crimes against humanity over Mr Duterte's deadly anti-drugs crackdown during his time as president and while mayor of Davao in the southern Philippines.
A panel of judges will confirm whether there is sufficient evidence to proceed to a formal trial.
Mr Duterte is the first Asian former head of state to be indicted by the ICC, accused of being an "indirect co-perpetrator" in dozens of murders that took place in the context of his so-called war on drugs.
In their opening statement, prosecutors told the court Mr Duterte committed crimes against humanity as part of a "widespread and systematic attack" on the people of the Philippines.
Prosecutors said Mr Duterte authorised murders, provided resources, offered incentives and created and maintained a system of protecting perpetrators.
The pre-trial is examining three counts of crimes against humanity, including two crimes of murder relating to the Davao Death Squad, and the murders of "high-value targets" while Mr Duterte was president.
"[These] were not random crimes, nor were they spontaneous or happened in isolation," ICC prosecutor Mandiaye Niang told the court.
"The evidence demonstrates they were part of a widespread and systematic attack directed against the civilian population of the Philippines."
Mr Niang told the court that Mr Duterte's war on drugs resulted in the killings of thousands of civilians.
"Many of these victims were children," he said.
"The victims of extrajudicial killing charges were brutally murdered, some after being abducted and mistreated.
"The loss of every single one of these victims had the most profound impact on their families, their friends and their communities."
Lead defence lawyer Nick Kaufman told the judges that Mr Duterte "stands behind his legacy resolutely, and he maintains his innocence absolutely".
According to Mr Kaufman, the prosecution "cherry-picked" examples of Mr Duterte's "bombastic rhetoric", and his client's words were never intended to incite violence.
Estimates of the death toll during Mr Duterte's presidential term vary, from the more than 6,000 that the national police have reported to up to 30,000 claimed by human rights groups.
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Mr Duterte, who is 80, was arrested in March last year and flown to The Hague.
His trial was delayed, with his lawyers arguing he was in poor health and deteriorating while in court detention.
The ICC last month declared he was fit to stand trial, however Mr Duterte was not present on Monday, after waiving his right to appear at the pre-trial.
Outside court, protesters held signs and called on the ICC to hold Mr Duterte accountable.
"Duterte is a coward for choosing not to show up in front of the families of victims, for trying to evade accountability and justice," one woman told Reuters.
Activists and families also held protests in Manila on Monday, with dozens of relatives of those killed in Duterte's war on drugs gathering to watch the pre-trial together.
"We're hoping that the ICC, even if it's thousands of miles away, will finally render justice to all these families," said Randy delos Santos, a volunteer in a charity shelter that was hosting one event.
Supporters of the former president have lobbed criticism of sitting Philippine President Ferdinand Marcos Jr for arresting Mr Duterte to be sent to The Hague.
In the lead-up to the pre-trial, Mr Duterte's daughter, current Vice-President Sara Duterte, announced she was running for president in 2028.
The ICC judges will sit for pre-trial hearings this week, before taking a maximum of 60 days to confirm whether charges against Mr Duterte will proceed.
ABC/wires