A concert to honour anti-Apartheid hero Nelson Mandela set to take place over the weekend in the Spanish capital has been postponed, a spokeswoman for the host venue said Thursday. The concert was planned at Madrid's Las Ventas bullring on Sunday on Mandela's 92nd birthday but it will now take place in October, she said. No reason for the delay was given. Madrid was chosen by Mandela's AIDS charity 46664 -- the number that adorned his prison uniform during his 27 years of captivity on Robben Island -- to host the annual concert in honour of the former president. Organisers had promised that top celebrities would attend but no names were divulged. In November a UN resolution officially declared July 18 to be International Nelson Mandela Day. Last month legendary blues guitarist B.B. King performed a free concert in honour of South Africa's first black president in Madrid to kick off International Nelson Mandela Day celebrations in Spain. The idea of holding an annual Mandela concert was born following the huge international success of the celebration of his 90th birthday in London in 2008. The following year, unofficial 'International Mandela Day' celebrations took place in New York, featuring performances by Stevie Wonder, Alicia Keys, Aretha Franklin and France's singer-first lady Carla Bruni. 