The attacks in Brussels hit major stock indexes in early trading across Europe and the US, where investors were on tenterhooks over fears of a new wave of terrorism on the Continent and at popular travel destinations worldwide.

Belgian shares sank early in the day; so did the German DAX and the EuroStoxx50 indexes.

The STOXX Europe 600 Travel and Leisure index was also down, with shares in easyJet, Ryanair, Lufthansa, Air France and TUI all wavering. The British pound also fell amid fears that the explosions at the Zaventem airport and Maelbeek metro station could play a role in an upcoming referendum on Britain's membership in the EU.

But traders in Europe saw a lot of the losses pared as the day continued, with the FTSE-100 in London closing in positive territory, albeit only marginally (+0.1 percent). Germany's blue-chip DAX-30 ended the trading session up 0.42 percent, but many tourism and travel-related stocks remained in negative territory across Europe.

Across the Atlantic, US stocks also opened lower following the coordinated attacks in the European Union's de facto capital. Only minutes after the opening bell, the Dow Jones Industrial Average dropped by less than 1 percent. The S&P 500 and the Nasdaq Composite Index followed suit. The Dow closed down 0.23 percent, while Nasdaq was up 0.27 percent at the end of the session.

Tourism in an age of terrorism

The attacks in Brussels came only days after a suicide bomber hit a popular street in Istanbul, Turkey. It was the second terrorist attack on the city in as many months.

Last year was also rocked by violence, including a deadly shooting at a beach resort in Tunisia, a bomb that brought down a Russian passenger jet while it was flying over Egypt, killing everyone on board, and coordinated shooting and suicide bomb attacks in the French capital, Paris, which left 130 people dead.

"Geopolitical risk, including acts of terrorism which directly affect trade or movement, remains a significant risk factor to monitor," Lorne Baring, the managing director of B Capital Wealth Management in Geneva, told Reuters.

cjc/hch (AFP, Reuters, dpa)