The UN's cultural agency UNESCO Monday recommended that Venice be added to its list of world heritage in danger, saying the Italian authorities needed to step up efforts to secure the historic city and its surrounding lagoon.

UNESCO said in its recommendation that Venice risked "irreversible" damage due to a string of issues ranging from climate change to mass tourism. The recommendation will go to a meeting of UNESCO's World Heritage Committee in Riyadh in September for adoption.

"The effects of the continuing deterioration due to human intervention, including continuing development, the impacts of climate change and mass tourism threaten to cause irreversible changes to the outstanding universal value of the property," said UNESCO.

"Some of these long-standing issues have already led to the deterioration of the inherent characteristics of the property and its attributes," UNESCO said, warning that developments including high-rise buildings risk "having significant negative visual impact".

"Moreover, the combined effects of human-induced and natural changes are causing deterioration and damage to build structures and urban areas," it added.

It said that overall, there was a "lack of significant progress" by Italy in addressing these issues and this was further "hindered by a lack of overall joint strategic vision".