LONDON (AFP) - Airline and travel stocks tumbled across Europe on Tuesday (March 22) following deadly explosions at the airport and metro in Brussels, pushing stock market indices into the red.

After falls of between 1.0 and 1.5 per cent for Europe's main indices as news of the explosions first filtered through, the region's stock markets were showing losses of around half a percent nearing midday.

The euro fell against the dollar, while haven assets gold and the yen gave up earlier gains.

"While travel stocks had their knee-jerk reaction sell-off and safe havens were bid (higher), relative calm has quickly returned," said Mike van Dulken, head of research at Accendo Markets.

Belgian firefighters on Tuesday said there were at least 21 dead after "enormous" blasts hit Brussels airport and the city's metro system.

Around 1000 GMT (6pm Singapore time), London's benchmark FTSE 100 index was down 0.4 per cent, while in the eurozone, Frankfurt's DAX 30 fell 0.5 per cent and the Paris CAC 40 dropped 0.3 per cent.

Sentiment was boosted later in the morning by data showing that German investor sentiment had risen slightly this month.

In London, shares in tourism groups Thomas Cook and TUI slid 2.8 per cent and 3.2 per cent respectively, while InterContinental Hotels Group shed 2.0 per cent.

Easyjet dropped 3.1 per cent and IAG, parent of British Airways and Iberia, gave up 3.5 per cent in value.

French hotels group Accor meanwhile lost 3.3 per cent and German airline Deutsche Lufthansa retreated 2.0 per cent.

"The explosions are bad news for airlines which have just started to see passenger demand pick up again after a slump in the wake of multiple terrorist incidents at the end of last year, including the attack on Paris," said Jasper Lawler, analyst at trading group CMC Markets.

"The response from authorities is likely to be another extension of security controls which make travel even less attractive for tourists."