By JUAN FORERO

BOGOTÁ, Colombia, June 7 - Thousands streamed into the Bolivian capital, La Paz, on Tuesday as Indian protests against the ruling elite gained force even after President Carlos Mesa offered his resignation.

The critical highway to the highlands, where the international airport is situated, remained cut off by roadblocks, and the city of one million people was hit by food shortages and a transport strike.

Demanding that the government expropriate foreign energy installations and call new elections, miners in hard hats and indigenous women in derby hats and colorful, multi-layer skirts marched into La Paz in a show of force punctuated by blasts of dynamite that demonstrated the depth of the crisis buffeting the government.

The police fired at the protesters with tear gas, rubber bullets and water cannons, photographers at the scene said by phone from La Paz. Soldiers armed with rifles were, for the first time, patrolling the streets and guarding the seat of power in La Paz's main square, Plaza Murillo.

In Fort Lauderdale, Fla., where the Organization of American States was meeting on Tuesday, Bolivia's foreign minister, José Ignacio Siles, asked the member nations for a resolution pledging to "support the person who, in accordance with constitutional succession procedures, takes over the presidency" of Bolivia, according to Agence-France Presse.

Mr. Mesa submitted his resignation Monday night, and Congress is widely expected to accept it at an emergency session on Wednesday - if adequate security can be provided.

If Congress accepts Mr. Mesa's resignation, it must then decide who will finish out his term, which would have ended in August of 2007.

The two men next in line, the presidents of the Senate and lower house of Congress, are not acceptable to the protesters. But opposition leaders have indicated they would accept the third in line, the president of the Supreme Court, Eduardo Rodríguez, who has said he would take the post only to preside over early elections. Those could be held as early as August.

New elections have been demanded by Evo Morales, the congressman and indigenous leader who is head of the Movement Toward Socialism and is considered among the top candidates for president in the country of nine million. Mr. Morales, an Aymara Indian who gained prominence leading coca farmers protesting American-backed eradication efforts, seemed to be supporting nationalization of the energy industry.

"If we do not recover the natural resources for the Bolivian state we will never resolve the social, political and economic problems," he told CNN en Español late on Monday. "The oil fields should pass over to the Bolivian state."

The president of the senate, Hormando Vaca Diez, tried to reassure Bolivians on Tuesday, saying there was no vacuum of power. "President Mesa is still in the palace," he said late Monday night.

Indeed, Mr. Mesa, in his late-night televised speech to the nation on Monday night, assured Bolivians that he would remain in charge until Congress acted. Bolivia's previous president, Gonzalo Sánchez de Lozada, fled Bolivia after resigning in the face of violent protests in October 2003.

"It's not in my plans to travel to Miami or Washington," Mr. Mesa said. "That's my responsibility. You have a president who always shows his face and will be in the place where he has to be until the moment he completes his obligation."