A heavy cloud of smoke and the acrid stench of burning metal lingered over downtown Los Angeles on Sunday afternoon, as protesters clashed with law enforcement officers for a third day during a large-scale demonstration over immigration policies and deportations.

The downtown area, punctuated by the wail of sirens, helicopters circling overhead and sporadic explosions of police flash-bang grenades, transformed the usually bustling city into what some described as an "apocalyptic" scene.

The protests, sparked by recent immigration raids and detentions conducted by US Immigration and Customs Enforcement agents, escalated after demonstrators attempted to block a major intersection near the Metropolitan Detention Center in downtown LA, where many detainees are being held.

After protesters began throwing objects and attempted to push through police lines, law enforcement officers in riot gear responded with tear gas, batons and rubber bullets.

Amid the chaos, at least three self-driving Waymo vehicles were vandalized and set ablaze. Demonstrators smashed the vehicles' windows before setting them on fire. Flames quickly engulfed one vehicle as onlookers chanted slogans, many capturing the fiery scene on their phones.

Videos shared on social media showed the charred remains of the self-driving vehicles smoldering as night fell on the city.

Around the Metropolitan Detention Center and the LA City Hall, tension escalated as protesters squared off against authorities including mounted police. Demonstrators hurled debris such as fragments of concrete, rocks, glass bottles and fireworks at the officers. Some protesters threw objects repeatedly, drawing cheers from the crowd.

Armed officers held their ground until the crowd surged forward. The authorities then deployed crowd control weapons including rubber bullets and tear gas, which eventually forced the protesters to retreat.

The charred remains of cars, spent tear gas canisters and shards of glass littered the streets.

"This is not just about immigration," said one protester, identified only as Luis, who held a sign that read, "Let our neighbors go through US". "This is about who gets to belong in this country. This government doesn't represent the people anymore. America was built by immigrants, and we should be opening our doors, not shutting them," Luis added.