About 30 fans have been injured during a stampede at a concert by controversial rapper Eminem.

One man suffered a heart attack and four others needed hospital treatment after the star came on stage at the WHFS music festival in Washington DC.

The others were treated at the scene for minor injuries.

Concert-goers said the atmosphere had grown volatile and fans surged towards the stage when the rapper appeared.

Critical

"There were fights and a lot of pushing and shoving," said one witness, Brent Turner, 17, from Damascus, Maryland.

Eminem had insisted that the crowd calm down before he continued performing.

The heart attack victim was in a critical condition after being admitted to hospital on Saturday.

Paramedics were called to the festival again the following day when one man fell from the upper deck of the RFK Stadium. He was also in a critical condition.

Pirates

The festival draws 60,000 people a year, and also included performances from 40 other artists including The Strokes, Papa Roach and NERD.

It was the first full show Eminem had given to promote his new album, The Eminem Show, which was released on Sunday, 26 May, in the United States, and on Monday in the UK.

Its release had been brought forward by one week after internet pirates made it widely available to download for free.

The first single from the album, Without Me, was a new entry at number one in the UK chart on Sunday.