BERLIN - Switzerland has halted all "repatriation flights" for rejected asylum seekers after a Nigerian man on hunger strike died in police shackles at Zurich airport as he was being forced towards a plane that was about to deport him.

The 29-year-old man, who was a convicted drug dealer, had been on hunger strike for several days. Police said he collapsed on the tarmac and they immediately took off his shackles and called a doctor who tried to revive him.

The Swiss authorities said yesterday they had launched an investigation into the deportee's death. It was witnessed by 13 other Nigerians who were being deported with the man who died. They accused the police of inhumane treatment.

"They dealt with us like animals," one, named only as Emmanuel, told Switzerland's Swissinfo website. "The shackled our feet, knees, hands, hips arms and torso and made us wear a helmet like those worn by boxers. It was simply impossible to move."

It was the third death of a Swiss deportee since 1999. Last year Switzerland deployed 43 so-called "repatriation flights" which deported 360 people, mainly to Africa and the Balkans.

Switzerland voted in a referendum in favour of measures which tightened the country's already stringent immigration laws. The United Nations High Commission for Refugees called the vote "regrettable" and said it had left Switzerland with some of the toughest asylum laws in Europe. The UNHCR singled out Switzerland's insistence that asylum seekers should come up with identity documents within 48 hours or face deportation. It said many refugees were deprived of identification by the countries they had fled from.