From flames to fiery opposition, protests rock Ukraine, Venezuela, Thailand

  Catherine E. Shoichet. Jethro Mullen and Greg Botelho

(CNN) -- Demonstrators pack public squares. Flames shoot into the air. Tear gas sends crowds scrambling.

Dramatic scenes are unfolding during anti-government protests in three disparate countries this week, on three different continents.

The images are striking, and things are heating up quickly. What's happening on the ground?

Here's a cheat-sheet guide to the protests in Ukraine, Venezuela and Thailand

Ukraine

What are protesters' demands?

Who's a better economic ally, Europe or Russia? That's the key issue at the heart of Ukraine's protests. Demonstrators want the government to forge closer ties with Europe and turn away from Russia.

But the dispute is also about power. Many in the opposition have called for the ouster of President Viktor Yanukovych and the ordering of new elections. And both on the streets and in parliament, they've also pushed to alter the government's overall power structure, feeling that too much of it rests with Yanukovych and not enough with parliament.

Who's protesting?

An opposition coalition has been leading the charge against Yanukovych and his allies.

On CNN iReport, protesters and onlookers have shared more than 100 photos and videos of clashes between demonstrators and police. The nighttime images are especially striking -- figures are silhouetted against large bonfires set alight in the streets.

When did demonstrations start?

In November, thousands spilled onto the streets after Yanukovych did a U-turn over a trade pact with the European Union that had been years in the making -- with Yanukovych favoring closer relations with Russia instead.

What's the latest?

Long-simmering tensions exploded anew in Ukraine as clashes between police and anti-government protesters left more than 25 people dead and the capital's central square on fire into early Wednesday.

On Wednesday, U.S. Secretary of State John Kerry will raise the possibility of sanctions against the Ukrainian government in remarks in Paris, a senior administration official told CNN.

Also Wednesday, French President Francois Hollande said the violence and crackdowns in Ukraine are "unspeakable, unacceptable, intolerable acts." "Those who committed violent acts have to know they will be sanctioned," Hollande said.

VENEZUELA

 Photos: Protests erupt in Venezuela

What are protesters' demands?

Demonstrators are demanding better security, an end to goods shortages and protected freedom of speech.

They blame Venezuela's government, led by President Nicolas Maduro, for those problems. Maduro and other officials blame the opposition for the country's security and economic problems.

Who's protesting?

Many demonstrators across the country are students. Prominent opposition politicians have also led protests and joined marches.

Since February 13, more than 1,100 images have been uploaded to iReport, CNN's user-generated platform. Many of the videos and photos are gruesome and depict violent scenes between demonstrators and police.

When did demonstrations start?

Nationwide student protests started this month. On February 12, the demonstrations drew global attention after three people were killed.

What's the latest?

As throngs of supporters chanted their support, opposition leader Leopoldo Lopez turned himself in to authorities Tuesday. He faces charges of terrorism and murder connected with violence during the protests. Lopez has denied the charges. Maduro, meanwhile, has called members of the opposition fascists and compared them to an infection that needs to be cured.

THAILAND

Photos: Protests in Thailand's national election

What are protesters' demands?

Protesters in Bangkok have been calling for months for the ouster of Prime Minister Yingluck Shinawatra, whom they allege is a puppet of her billionaire brother, the deposed, exiled former Prime Minister Thaksin Shinawatra.

Who's protesting?

Opposition to Thaksin and Yingluck is strongest among the urban elites and middle class. That's why the demonstrations have been concentrated in Bangkok. The protesters want to replace Yingluck's government with an unelected "people's council" to see through electoral and political changes.

Thailand residents and visitors have shared dozens of stories of unrest on CNN iReport over the past month. The latest approved photos show demonstrators sleeping in the streets in Bangkok as a form of peaceful protest.

When did demonstrations start?

Protests began in November after Yingluck's government tried to pass an amnesty bill that would have paved the way for her brother's return to the political fray.

What's the latest?

Deadly violence erupted in the heart of Bangkok Tuesday as anti-government protesters clashed with police, and the country's anti-corruption commission filed charges against the Prime Minister.