As it was in medieval Hamelin, so it is today in the South African township of Alexandra: wherever you go, you are never far from a rat.

But residents of the Johannesburg suburb have been offered a deal unavailable in the era of the Pied Piper – a free mobile phone for every resident who catches 60 of the rodents.

Alexandra has just turned 100 years old and was the young Nelson Mandela's first home when he moved to Johannesburg. Its cramped shacks and illegal rubbish dumps sit in brutal contrast with neighbouring Sandton, dubbed the wealthiest square mile in Africa.

The crumbling structures, leaking sewage and discarded piles of rotting food are a perfect breeding ground for rats, much to the torment of residents. There have reportedly been cases of children's fingers being bitten while they sleep.

In an attempt to fight back, city officials have distributed cages and the mobile phone company 8ta has sponsored the volunteer ratcatchers.

Resident Joseph Mothapo says he has won two phones and plans to get one for each member of his family. "It's easy," he told South Africa's Mail & Guardian newspaper, wielding a large cage containing rats. "You put your leftover food inside and the rats climb in, getting caught as the trap door closes."

But there were signs that the PR stunt could backfire, as animals rights activists criticised the initiative on social networks.

On Monday 8ta denied responsibility for the initiative. It said it was a long-time sponsor of a charity called Lifeline, which had taken the decision to hand out phones.

"You will have to ask Lifeline why they decided to use these promotional products," said Pynee Chetty, an 8ta spokesman. "They do a lot of good community work, including in Alexandra. They used the promotional material to incentivise members of the community. I wasn't aware this is how they were going to resolve the problem [of rats]."

He added: "We won't distance ourselves from Lifeline. It is a charity that does a lot of good work and our support for them is steadfast. I don't want to deny the story. What I'm saying is that it's not our initiative."

The Mail and Guardian reported that thousands of rats have been gassed to death by a specialist, Ashford Sidzumo, at the local sports centre. "We record all the people's details so we can see where the rats are causing the biggest problem," he was quoted as saying. "We use this to send fumigation teams there."

Local councillor Julie Moloi told the Mail & Guardian there had been no choice but to carry out the drastic experiment. "We are afraid these rats will take over Alex and it will become a city of rats," she said.

In another measure, owls have been given to three local schools because of their rat-catching prowess. But wider deployment of the birds may be difficult: Moloi said people kill them because of traditional beliefs that they are to be feared.