Archaeologists in Peru have unearthed four mummies of children believed to be at least 1,000 years old from what was once a sacred ceremonial space that is now in one of the oldest neighbourhoods of modern-day Lima.

Researchers believe the children, discovered on Monday alongside the remains of an adult, come from the Ychsma culture that developed on Peru's central coast before the Inca Empire rose to span swathes of the Andean region.

Some remains were found at the foot of a staircase on a small hill which is believed to have once hidden a temple. Luis Takuda, an archaeologist in Lima's Rimac district, said the temple was likely built 3,500 years ago.

"This whole area is a very important ceremonial chamber," Takuda said. "The people who lived here during the Ychsma period still considered it a sacred space and therefore buried their dead here."

Takuda said the mummies' skulls still had hair on them. The remains were found alongside ceramics.

With a population of about 10 million, the Peruvian capital is home to some 400 archaeological ruins.