President Carlos Mesa offered to resign Monday night, seeking to quell weeks of anti-government protests that have paralyzed parts of the country.

The offer came as tens of thousands of Indians, miners and other workers protested in downtown La Paz in their largest anti-government march in weeks.

"This is as far as I can go," Mesa said in a nationally televised address. "It is my decision as president to present my resignation." It was the second time this year he offered to step down because of street protests.

Protesters had been calling for Mesa's resignation as well as demanding earlier elections. Monday's protests in La Paz were largely peaceful, but riot police fired volleys of tear gas canisters and fought sporadic battles against rock-throwing protesters on the fringes of the demonstration.

More than 500 protesters were turned away by acrid tear gas as they tried to close in on Mesa's seat of power at Government Palace, and riot police also scattered a crowd of thousands from another downtown plaza when they tried to rally.

No injuries were immediately reported, but police made 22 arrests, among them protesters accused of brandishing dynamite, according to Channel 7 state television.

Mesa previously offered to resign in March amid similar protests, in an apparent political gamble to rally critics around his administration. Lawmakers rejected the offer then, giving Mesa crucial support after he had said the country was becoming ungovernable.

The crisis pits Indian and labor groups from the poorer eastern highlands, including La Paz and its poor satellite city of El Alto, against ruling blocks from Santa Cruz in the east and the oil-rich gas fields to the south that are pursuing greater autonomy.

The protests have steadily increased after Bolivia's Congress moved last month to increase taxes on foreign oil companies that have flocked to the country to develop its natural gas reserves -- the second-largest in South America after Venezuela.

Tens of thousands of protesters, some waving wooden weapons, paralyzed downtown La Paz, Bolivia's capital, in their largest anti-government march in weeks. Most protesters were peaceful.President Carlos Mesa was forced to flee his office as protesters threatened to overwhelm guards.