JOHANNESBURG (AP) — South African police arrested nine people during arson attacks and stone-throwing near a Johannesburg university where students have been protesting for free education, authorities said Saturday.

Two vehicles were set on fire in the overnight unrest in Braamfontein, an urban area that was the scene of similar violence during clashes between students and police earlier in the week, the national police said on Twitter.

Of the nine people arrested, two are students at the University of the Witwatersrand, also known as Wits, two are from other universities and five are not students, said Shirona Patel, a university spokeswoman.

The school, one of South Africa's leading universities, has imposed overnight restrictions on access and movement on campus because of security concerns. It rejected criticism from some protesters that additional security measures and a police presence on campus were provoking violence.

"The only reason these measures were implemented was because a group of students started four fires on our campuses on Thursday night, smashed windows, stoned buildings and flooded rooms," the university said in a statement Saturday.

In other violence, two buildings were damaged by firebombs at the Howard College campus of the University of KwaZulu-Natal, South African media reported Saturday.

Student protests, many of which have turned violent, have forced some South African universities to close. The unrest began last month when the government recommended that universities increase 2017 fees by no more than 8 percent, while saying it would cover fee hikes next year for poor university students.

Protesters, however, say the plan is insufficient and demand the gradual implementation of free university education. Large student protests in 2015 forced the government to freeze fee increases this year.

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