Officially, 500 people died, but rights groups claim the true number was in thousands when 27,000 US soldiers invaded Panama with the backing of fighter planes, tanks and heavy artillery.
Panama has observed a day of national mourning for the first time ever to mark the anniversary of the US invasion in 1989 to oust dictator Manuel Antonio Noriega.
"We pray for the fallen, looking upward and moving forward together," President Laurentino Cortizo said on Tuesday at a ceremony attended by some 300 relatives of victims, government officials, diplomats, soldiers and activists.
The national flag flew at half-mast between rows of marble plaques in the Peace Garden Cemetery in Panama City that holds the remains of dozens who died on December 20, 1989, when 27,000 US soldiers invaded the country with the backing of fighter planes, tanks and heavy artillery.
They came to depose Noriega, wanted by a Miami court to face accusations of drug trafficking.
Officially, 500 people died, but rights groups claim the true number was in the thousands.
Among the dead buried in the Peace Garden are children such as Tomas Palacios, who was just 10 when he died.
At least 200 of the fallen were civilians.
"Time has not finished healing this wound," said Trinidad Ayola, a representative of families who lost loved ones.
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Noriega, who ruled from 1983 to 1989, surrendered in January 1990 and was jailed for drug trafficking and the disappearance of opponents in the United States, France and Panama.
After prison stints abroad, he died in Panama in 2017.
The Inter-American Commission on Human Rights in 2018 found the United States guilty of "human rights violations" and ordered it to "provide full reparation."
Victims have demanded that Washington recognise the invasion, compensate the country and provide information about mass graves.
In March, Panama's Congress approved the declaration of December 20 as a day of national mourning.
Efforts continue to find and exhume victims from mass graves.
Many Panamanians applauded the US invasion as it ended two decades of military dictatorship and opened the door to democratic elections.
Some, however, believe Operation Just Cause failed to delay the handover of joint US-Panamanian control of the Panama Canal, critical to international trade, to Panama in 1999 under an international agreement.
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