Iran Press/ America: Chilean President Sebastián Piñera said the decision had caused him "pain" but his government needed "to prioritize re-establishing public order".
The COP25 climate summit was scheduled for 2 to 13 December, while the Apec trade forum was next month, BBC reported.
The UN said it was now looking at alternative venues.
World leaders were to gather at this year's Conference of the Parties (COP) to discuss the implementation of the Paris Accord - a landmark international climate agreement, first signed at COP21 in December 2015.
This is the first time a country has pulled out of hosting the conference at such short notice.
In a statement, the UN's climate change executive secretary, Patricia Espinosa, said: "Earlier today, I was informed of the decision by the government of Chile not to host COP25 in view of the difficult situation that the country is undergoing. We are currently exploring alternative hosting options."
This is a huge blow to hopes of progress on what many see as the crisis of climate change.
Just as the science becomes more robust about rising carbon levels driving up temperatures and triggering a range of dangerous impacts, diplomats and experts have been looking to the COP25 talks in December as a vital staging post on the way to global action.
In particular, developing countries - the most vulnerable to the effects of rising sea levels and stronger storms - were banking on the event to raise their claims for more help from the richest nations.
But the longer the unrest has continued on the streets of Santiago, the more the government of Chile must have worried about coping. Already there were reports of delays in getting the massive conference venue ready for the tens of thousands of delegates and campaigners.
104/204
Read More
Chile's president declares a state of emergency after riots over metro fare hike
Terrorist explosion hits bus stop at busy Avenue in Chile's Capital
