Scores of disabled people on crutches and in wheelchairs fought police in La Paz, Bolivia's capital, over demands for better welfare support, injuring several and fuelling anger against the state.

A caravan of about 50 adults and children ended a 1,000-mile, 100-day trek through Bolivia at the protest near government offices in La Paz on Thursday. Scuffles broke out and pepper spray was used after the group were blocked by riot police, who stopped them reaching the legislature and presidential palace to petitioning MPs and the presidential palace for a tripling of the £91 monthly state subsidy for disabled people. The protesters tried to break through the lines using their crutches and wheelchairs but were forced back in a melee in which several people were injured and four detained. The protest organisers then declared a hunger strike by 10 adults and a round-the-clock vigil by the rest.

The clashes were another public relations PR fiasco for President Evo Morales, who has seen his once-huge popularity plunge amid protests from coca farmers, indigenous rights activists and environmentalists. Bolivia's first indigenous leader swept to power in 2006 promising to ease poverty and inequality, and was hailed a saviour in his first few years. But marches on La Paz – notably one over a controversial Amazon road in October – illustrate the level of disenchantment.

The disabled protesters relied on charity on their journey to the highland capital from Beni, bordering Brazil, in November. As well as higher subsidies, they want greater efforts to integrate them into a society that makes little provision for those with physical or mental disabilities.

Domitila Franco, a wheelchair-user, said she struggled. "It's very hard to be a person with a disability," she said. "Even our own husbands abandon us because they feel ashamed of us. … I look after my four children alone, washing and ironing clothes for people."

The protesters to end their trek at Plaza Murillo, the heart of government, having seen other marches do so. "Why not us?" Camilo Bianchi, a protest leader, asked local media. "It's a public space."

Carlos Romero, a government minister, told a press conference that opposition groups had infiltrated the march and it was necessary to block it. "There are other groups trying to politicise this, trying to create a climate of disorder and confrontation," he said. "Our obligation is to secure Plaza Murillo."