AFP reporters saw soldiers and tanks entering Plaza Murillo, a historic square where the presidency and Congress are situated. One of the tanks tried to break down a metal door of the presidential palace.

Bolivian television reported that army chief General Juan Jose Zuniga briefly entered the presidential palace before leaving on foot.

"We denounce irregular mobilizations by some units of the Bolivian Army," Arce wrote on the X social network. "Democracy must be respected."

It was unclear if he was in the presidential office.

Former president Evo Morales wrote on X that "a coup d'Etat is brewing."

"We call for a national mobilization to defend democracy," he said, adding the alleged coup was being planned by Zuniga.

Rumors have been circulating since Tuesday that Zuniga was on the verge of being dismissed.

The military official appeared on television on Monday and said he would arrest Morales -- Bolivia's first Indigenous president -- if he insisted on running for office again in 2025 despite being disqualified from doing so.

Morales was extremely popular until he tried to bypass the constitution and seek a fourth term in office in 2019.

The leftist and former coca union leader won that vote but was forced to resign amid deadly protests over alleged election fraud, and fled the country.

He returned after his ally-turned-foe Luis Arce won the presidency in October 2020.

Supporters of Morales in January set up days of road blockades to protest his disqualification.

The Organization of American States (OAS) also condemned the troop movements.

"The international community, the general secretariat of the OAS will not tolerate any form of breach of the legitimate constitutional order in Bolivia or anywhere else," said secretary general Luis Almagro.