By Jethro Mullen and Matt Egan

HONG KONG (CNNMoney) -- Global stock markets are sinking and the Mexican currency is plunging as initial results from the U.S. presidential election come in.

U.S. stock futures are plunging, with key battleground states too close to call between Donald Trump and Hillary Clinton.

Dow futures have plummeted 700 points, or 4%, Tuesday night. Stock indexes across Asia were also deep in the red. Japan's Nikkei plummeted nearly 5% and the Hang Seng in Hong Kong dropped around 3%.

Markets hate uncertainty -- and many investors believe Donald Trump's unpredictable nature and anti-trade stance could bring lots of global uncertainty if he wins the presidency.

"Shock and awe would aptly describe movements of global markets right now," said Matt Simpson, a senior markets analyst at ThinkMarkets.

Stock futures really began tumbling after 9 p.m. ET as it became clear that several key battleground states, including Virginia, North Carolina and Florida were too close to call.

"It wasn't supposed to be this close," said Nicholas Colas, chief market strategist at brokerage firm ConvergEx. "Regardless of how things shake out in an hour or two, this is a surprise -- a big surprise."

The Mexican peso has plunged more than 10% to an all-time low, after seesawing violently all evening as Trump started pulling ahead in key battleground states. Trump's anti-Mexico rhetoric has affected the value of the peso for weeks. Trump has talked about renegotiating or even ending NAFTA, the free trade deal between the U.S., Mexico and Canada.

"The Mexican economy is most tied to Donald Trump's criticism of global trade. It really is ground zero of this discussion economically," said Colas.

Investors turned to assets that are seen as safer bets in times of uncertainty. Gold jumped more than 3% and the Japanese yen surged more than 3% against the dollar.

"It is looking like another Brexit-type surprise," said Ryan Detrick, senior market strategist at LPL Financial. "The fear of uncertainty is taking fold, as the potential for a Trump victory has many taking a sell first and ask questions later approach."

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