MILAN, Italy

Protesters and police have clashed at the opening of the international EXPO 2015 fair in the Italian city of Milan - a global showcase of initiatives aimed at sustainably managing global food and energy resources.

Smoke drifted above the city after cars were set on fire and police fired water cannons and tear gas at demonstrators as a reported 20,000 people staged a "No Expo May Day Parade" in the city.

Some masked demonstrators threw stones and challenged police in riot gear and streets were blocked with burning rubbish bins.

Italian Prime Minister Matteo Renzi said in a speech as he opened the fair, in which representatives from 147 countries are involved, themed "Feeding the Planet, Energy for Life": "Many did not believe in us (Italy) and EXPO is realized today thanks to great efforts by all workers, both women and man."

The countries involved will reveal their technologies and commitment to creating sustainable ways of producing and delivering food across the globe while safeguarding the planet in the fair, which will end on Oct. 31.

'Economic crisis'

But protesters say Italian authorities are wasting public funds as the country plunges deeper into economic crisis and also claim the fair only benefits the corporations involved.

During his speech, Renzi touched upon the recent migrant tragedies in the Mediterranean Sea and brutal murder of university students in Kenya, saying all the countries at the Expo should embrace the whole world in their efforts to overcome its problems.

He thanked two people in particular - Milano's former mayor Letizia Moratti and former president Giorgio Napolitano - for their contribution to bringing the EXPO and its theme to Milano.  

Pope Francis connected to the fair via a live video conference and said the EXPO represented the "globalisation of solidarity" and invited "everyone" to the fair.

Turkish presence

Meanwhile, the flags of the 147 countries were flown at half-mast in respect of the more-than 6,000 victims of the earthquake in Nepal.

Turkey's Pavilion also grabbed attention from visitors at the EXPO. 

A Turkish delegation composed of Economy Ministry Undersecretary Ibrahim Senel, Turkey's EXPO 2015 High Commissioner Tarik Sonmez and Turkey's Consul General to Italy, Aylin Sekizkok, were present at the opening.  

EXPO officials said about 200,000 people visited the fair on the first day.