Protesters opposed to Donald Trump hurled rocks and bottles outside a Trump rally in New Mexico on May 24, the same day the bombastic billionaire won the Republican presidential primary in Washington state.

The primary victory brings Trump, the last Republican standing in the 2016 U.S. presidential race, one major step closer toward clinching his party’s nomination.

But the success was clouded by violent anti-Trump demonstrations in Albuquerque, New Mexico.

Chaos erupted outside a Trump rally when protesters threw burning t-shirts and bottles at police, and tried to storm the convention center where the provocative Republican candidate was speaking.

Horse-mounted police and officers wielding clubs used pepper spray and smoke bombs to try to disperse the crowd.

The protesters, several of whom waved Mexican flags, chanted expletives about Trump. Some also waved signs with expletive-laden anti-Trump slogans in Spanish.

Trump has proposed building a wall on the Mexican border, suggested that Mexican immigrants were rapists and drug dealers, and urged the deportation of the 11 million undocumented immigrants in the United States.

“Protestors are now throwing bottles and rocks at our Police Horses,” Albuquerque police tweeted.

The southwestern U.S. state has highest percentage of Hispanic residents – nearly 50 percent – of any other state, and polls show that Hispanics overwhelmingly oppose Trump’s immigration proposals.

Trump addressed a rally of about 4,000 people earlier on May 24, but was frequently interrupted by protesters, the Albuquerque Journal reported.

Police managed to stop a group of about 100 protesters who had tried to storm the convention center when Trump was speaking, the newspaper said. Riot police were deployed soon after.

Several Trump rallies have drawn protests, including in Chicago in March when his supporters clashed with protesters.

Trump has been criticized for inciting violence at his rallies.