Stocks markets around the world slid Friday as traders sought haven investments such as the yen and gold following an attack in Barcelona that sent airline share prices tumbling.

Thursday's deadly van attack in the Catalan capital compounded investors' concerns over economic policy paralysis in Washington.

"The recent shift towards haven markets continues," said Joshua Mahony, market analyst at IG trading group.

David Madden, analyst at CMC Markets UK, noted that "the combination of political uncertainty in the US and security concerns in Europe are weighing on investor sentiment".

In afternoon trading, the main stock indices in London, Paris and Madrid were each down 1.0 percent compared with Thursday's closing levels.

Gold, seen as a store of value in uncertain times, jumped back above $1,300 per ounze for the first time in nine months, while the yen strengthened against the dollar and struck a near-seven week high versus the euro.

"While the week started well, we are now seeing widespread selling for global