South African Afro-pop group Freshlyground was denied entry into Zimbabwe, an official said Monday, apparently over a song portraying President Robert Mugabe as a "chicken" afraid to relinquish power. Freshlyground flew into Zimbabwe on Sunday, where they were billed to perform as the main act at the Harare International Festival of the Arts (HIFA), but were turned back at the Harare international airport. "The group was sent back because they did not have a valid work permit," Francis Mabika, Zimbabwe immigration spokesman said. "Their permit had not been processed so they could not be allowed to enter the country." Mabika would not give details of why the permit was not processed. "Ask them (Freshlyground). They know the reasons why they were denied," he said. Freshlyground said on Twitter: "We regret to announce that we were denied entry into Zim today. 'reasons not given'. We are hugely disappointed. Cluck cluck cluck." Freshlyground was previously denied entry into Zimbabwe to perform at a concert after they released a song 'Chicken to change' poking fun at Mugabe, who has been in power since 1980. Zimbabwean fans of the popular group expressed their outrage at the latest ban on Twitter, where it was also pointed out that the song 'Chicken to change' had received thousands of new hits on Youtube. HIFA organisers were forced to call in other other groups to perform on Sunday evening. "Freshlyground arrived at Harare International Airport but will not be performing at HIFA this year," HIFA said in a statement released Sunday.