Jakarta – Protesters disrupted a concert by a US hip-hop artist touring Indonesia at the US Embassy's invitation, an embassy official and witnesses said Tuesday.

At around 8 p.m., more than 20 men on motorbikes rode through a crowd of 2,000 gathered to see New York-based hip-hop artist Toni Blackman and her three-member band perform at a university campus in the North Sumatra provincial capital of Medan.

The men then seized the microphone and yelled anti-American slogans, said Donna Welton, cultural attache at the US embassy in Jakarta.

Medan police said the protesters had previously been involved in anti-globalization protests, but could not confirm further details.

Blackman is on a US-embassy sponsored tour of Indonesia, the world's most populous Muslim country, from Jan. 28 to Feb. 3.

Blackman, dubbed by one US radio station as the "Ambassador of Hip-Hop," had just returned from Indonesia's tsunami-battered Aceh province, where she participated in a musical exchange with university students in the area.