A street vendor's cooking gas container exploded on Saturday night amid a Carnival celebration in the Bolivian city of Oruro, killing eight and injuring 40 others, police said.

The vendor, who was cooking deep fried llama rinds, had likely dripped hot oil onto the hose of the cooking gas container, prompting the blast, Oruro police chief Romel Raña said.

The accident took place on a crowded street not far from the main route of the festival's 4-km parade. Three children were killed and several others were in critical care, he said.

President Evo Morales on Saturday night expressed his condolences on social media.

"We are dismayed at the news of the deaths caused by the explosion," Morales wrote.

Oruro is a high-altitude city of 265,000 located about three hours southeast of the country´s capital of La Paz.

The city´s well-known Carnival festival, one of countless such celebrations throughout Latin America this weekend and early next week, is expected to attract upwards of 400,000 visitors from Bolivia and abroad, tourism officials said.

The 10-day festival includes as many as 6,000 musicians and thousands more dancers in bright-coloured masks and folkloric dress and was declared a cultural heritage site by the United Nations.