MEDELLÍN, Colombia — A former top commander of Colombia’s largest rebel group, the Revolutionary Armed Forces, vowed a return to war and issued a new call to arms on Thursday, almost three years after the rebels signed a peace deal to disarm.

The commander, whose real name is Luciano Marín but is known by the alias Iván Márquez, said in a video that his group, known as the FARC, would return to fighting because of what he called the government’s violations of the peace agreement.

The announcement could signal a shattering of the agreement, which ended a war that lasted 52 years, displaced millions from their homes, and left at least 220,000 dead.

Mr. Márquez was a crucial part of the peace talks three years ago, and now, by turning away from the deal, he could have an equally important role in tearing it apart.