Germany's Bundestag lower house of parliament approved a motion to strengthen the euro zone rescue fund via leveraging on Wednesday, providing Chancellor Angela Merkel with the mandate she needs to negotiate at a key euro summit later in Brussels.

The vice president of the lower house said 503 lawmakers had voted in favour of the motion, 89 had voted against and there were 4 abstentions.

The motion states that the European Central Bank (ECB) will no longer need to buy bonds on the secondary markets, and that the rescue fund cannot be financed through the ECB.

(Reporting by Alexandra Hudson and Annika Breidthardt)