Bolivia's defence minister has resigned in protest against a police crackdown on anti-highway demonstrators, increasing pressure on Evo Morales, the Bolivian president, over his handling of the situation.

Forty-one days into a march against government-supported plans to build a 300km highway through an Amazon rainforest reserve, police fired tear gas and briefly detained protesters in the Yucumo region on Sunday, prompting the minister's resignation on Monday.

Several people suffered minor injuries, according to local media reports, and the crackdown was criticised by opposition politicians, the ombudsman and several government officials, including Cecilia Chacon, the defence minister.

"This is not the way! We agreed to do things differently," Chacon wrote in her resignation letter, which was published by Bolivian media on Monday.

Ivan Canelas, the country's communications minister, said that police had no choice when responding to the protests.

"The march was defused because it had become a source of violence," he told the Reuters news agency.

Police surged into the demonstrators' camp with "extreme violence", veteran activist Maria Carvajal told the AFP news agency. "I could not believe what was happening."

On Monday, protesters reacted by setting barricades on fire on the airport runway in the town of Rurrenabaque, in an attempt to free about 300 marchers who were being held by authorities, Mayor Yerko Nunez told local media.

In La Paz, the capital, riot police set up a security cordon around the Quemada government building, as thousands of demonstrators gathered outside to protest the crackdown.

Other protests were also held in the central city of Cochabamba, where students marched and majority Aymara and Quechua indigenous peoples began a hunger strike.

Protests were also held in the northern province of Beni and in Santa Cruz.

Split in ruling party 

Morales, Bolivia's first indigenous president, put the controversial $420m highway - mostly funded by Brazil's government - at the heart of his infrastructre plan for the country.

The highway has elicited fierce opposition, however, from local indigenous leaders, who traditionally support Morales. The split has exposed differences within Morales' Movement Toward Socialism party.

Some MAS lawmakers have expressed support for the demonstrators and the demands of the 12,000 residents of the Isiboro Secure Indigenous Territory and National Park, through which the proposed road would be built.

In June, Morales angered activists by saying that the road would be built through the territory "whether they like it or not".

Seeking to defuse tension over the issue, Morales said on Sunday that a referendum would be held in the provinces affected by the highway's construction, "so the people can decide whether the project should go ahead or not". Further details on the referendum were not available.

Morales is highly popular among the Quechua and Aymara indigenous majority in the Andean highlands, but opposition to his policies is strong in the eastern lowlands, even among indigenous groups.

Fallout from the unrest could put him in a defensive posture for the nationwide judicial elections in October, which are part of broader reforms put in place to give indigenous people more political power.

Source: Agencies