Kosovo's former president pleads not guilty as war crimes trial begins
He faces 10 charges stemming from the 1998-99 insurgency that eventually led to the region's independence from Serbia.
"I understand the indictment and I am fully not guilty," he told judges shortly after hearings began.
The one-time guerrilla hero allegedly targeted perceived enemies of the ethnic Albanian Kosovo Liberation Army (KLA), including Serbs and Roma, as the rebels sought to seize power.
Prosecutors say Thaci, who went by the nickname "Snake" during the war, is jointly responsible for more than 100 murders by the KLA ranging from executions to deaths of mistreated detainees.
The trial of Thaci, 54, and three other men starts at 0700 GMT on Monday and will hear opening statements from the prosecution and lawyers for the victims. Defence lawyers will speak from on Tuesday.
They each face six counts of crimes against humanity and four counts of war crimes, including murder, torture, forced disappearances, persecution and cruel treatment.
The other defendants are former KLA spokesman Jakup Krasniqi, Thaci's closest political ally Kadri Veseli and key KLA figure Rexhep Selimi.
Thaci pleaded not guilty at a hearing in 2020. He had resigned as president by that time and handed himself in to the EU-funded Kosovo Specialist Chambers in the Netherlands after he was charged.
The indictment accuses Thaci and his co-defendants of being "part of a widespread and systematic attack against persons suspected of being opposed to the KLA", the court said in a statement.
The victims include "hundreds of civilians and persons not taking part in hostilities". The charges date between March 1998 and September 1999 and involve several locations in Kosovo and northern Albania.