UPDATE 2-EU court: governments cannot force telecom firms to store all data

* EU court struck down EU-wide data retention law in 2014

* Britain and Sweden had challenged that ruling

* Targeted retention to fight serious crime allowed - court (Adds Privacy International commment)

BRUSSELS, Dec 21 (Reuters) - EU countries cannot force telecom operators to keep all their customers' data, the EU's top court ruled on Wednesday, weighing in on a privacy debate that has raged since Edward Snowden's 2013 leak on mass surveillance by British and U.S. spies.

Attacks in Europe from France to Belgium - and, on Monday, in Berlin - have reinforced calls for security agencies to be given greater powers, while privacy advocates say mass retention of data is ineffective in the fight against such crimes.

The Court of Justice of the European Union (ECJ) said its ruling was based on the view that holding traffic and location data en masse allowed "very precise conclusions to be draw