Tourism stocks have plunged further after several explosions hit Brussels in what are suspected to be terror attacks.

On the FTSE 100, airlines EasyJet and Ryanair were both down by more than 4%. British Airways owner International Airlines Group plummeted by almost 5% on Tuesday morning (22 March 2016). Air France KLM dropped 4.6% on Tuesday. European stock markets all sunk, something that often occurs after a large-scale attack.

Several news agencies are reporting that 13 people have been killed and 35 severely injured in the attack on Brussels airport. Many flights have been diverted in response, and the airport has been evacuated and closed down. After further blasts on the city's Metro system, most public transport has been closed off as well.

In the UK, the FTSE 100 fell by almost 1% in morning trading, while Brussels' own BEL 20 dropped by 1.6%. Both Amsterdam's AEX and the CAC 40 in France dropped by more than 1.4%, while the German DAX plunged by 1.75%.

Tourism stocks across the continent dragged down the stock markets, with airlines and groups such as Intercontinental Hotels (down by 3%) weighing on the FTSE 100. Tour operator Thomas Cook's share price dropped by more than 4.6%, after it warned in its results that terror threats are hurting the tourism sector. Thomas Cook's rival Tui dropped by almost 3%.

"No surprise to see European airlines and travel shares being offloaded this morning while Gold and the Yen benefit from fresh safe-haven seeking," Michael van Dulken, head of research at Accendo Markets, commented on the events. "Investors have had to develop a thick skin for such horrific events over the years, and their encouraging defiance may again result in near-term recovery for the stocks affected."

Foreign Exchange traders are keeping their eyes on the euro, which slid by 0.6% against the pound to €1.27. Eurostar initially said it is continuing its services as usual, but warned of delays at its Brussels station. The company later said Brussels services were suspended.