At least 10 langurs have been on duty outside some of the venues in the Indian capital, reports say.
Delhi civic authorities have 28 langurs and 10 more have been brought in from the neighbouring Rajasthan state.
Thousands of monkeys roam Delhi, mostly around government offices and are considered a public nuisance.
Langurs are an aggressive type of monkey with long tails and dark faces. They are controlled on leads by specially trained handlers, who release them once other monkeys are seen.
The boxing and hockey stadiums are seen as particularly vulnerable to the monkey menace, the AFP news agency quoted a civic official as saying.
Four langurs will patrol the two stadiums, he said. Two more would be on standby, he added.
“They are there for the monkey problem. They will be moving outside the stadiums,” AFP quoted New Delhi Municipal Committee official Devender Prasad as saying.
For years the animals have caused havoc, riding on the city’s metro trains and even roaming through parliament.
They have invaded the prime minister’s office and the defence ministry.
They cannot be killed because many Indians see them as sacred.
After one of the strongest monsoon seasons in years, Delhi is also struggling with a major dengue fever outbreak caused by mosquitoes that breed in standing water.
Fish that eat mosquito larvae have reportedly been put in the pond in the Games Village to protect athletes from dengue, a viral infection transmitted to humans by the female Aedes mosquito. — BBC.