LOS ANGELES (Reuters) - Hundreds of people marched through Los Angeles on Sunday (May 1) in May Day rallies that took aim at Republican presidential front-runner Donald Trump for his campaign vow to build a wall along the United States border with Mexico to stop illegal immigration.

The rallies in a city with a large immigrant population come just days after protesters smashed the window of a police car and blocked traffic in chaotic scenes outside a Trump campaign event in Costa Mesa, California, 64km south-east of Los Angeles.

On Friday, demonstrators who blocked the entrance of a hotel hosting the California Republican convention in Burlingame, south of San Francisco, forced Mr Trump to halt his motorcade and go through a back entrance to deliver his speech.

Three separate marches were planned in Los Angeles on Sunday and began peacefully around noon, with several hundred people championing a variety of causes, including immigrant and worker rights.

But members of the boisterous crowd also carried a large blow-up doll of Mr Trump holding a Ku Klux Klan hood and signs that read: "Dump Trump."

Protests have become common outside rallies for Mr Trump, 69, the New York billionaire businessman.

He has aroused criticism for his pledge to deport all the country's illegal immigrants, even as it helped propel him in the race for the Republican nomination for the Nov 8 election to succeed Democratic President Barack Obama.

He has accused Mexico of sending drug dealers and rapists across the US border and has promised to build a wall along the southern border and make Mexico pay for it.

Mr Trump said on Sunday he will have essentially sealed the Republican nomination if he wins Tuesday's contest in Indiana, where he holds a big lead over chief rival Ted Cruz, a US senator from Texas.

California holds its presidential primary on June 7.