Around 100 emergency services workers were searching Monday for a two-year-old boy who fell into a narrow, deep well in southern Spain, officials said, in a race against time that has gripped the country.

The toddler, who has not been formally identified, tumbled into the 110-metre deep shaft in a mountainous area near the town of Totalan on Sunday while playing as his parents had lunch nearby, family members told local media.

Firefighters have so far only found a bag of sweets in the well - which is just 25 centimetres (10 inches) wide - that the child was carrying when he went missing, said Maria Gamez, Spain's government representative in Malaga province.

"It's cold, humid, its not easy to carry out a search there...Nobody is prepared technically to rescue a body from such a narrow space," she added.

Rescuers are trying to avoid blocking the well with falling soil as they search for the boy, Gamez said.

Two cameras lowered into the well had failed to capture any trace of him.

The well had been bored a month earlier during water prospection works and was not covered or protected, according to local media reports.

The boy's parents are "devastated" and were getting counselling from a team of psychologists, Elena Trigo, a spokeswoman for emergency services in the southwestern region of Andalusia, told public radio RNE.

The rescue operation will continue until he was found, she added.

Rescue teams were reportedly considering digging a hole parallel to the one the youngster fell down to try to reach him.

Spanish television and radio stations followed the search operation closely and Prime Minister Pedro Sanchez said on Twitter that he shared "the anguish" of the boy's family.

"All my support for the parents and the emergency teams who are participating in the rescue. We continue to hope for the best outcome," he added.