BERLIN, April 6 (Xinhua) -- The German federal government expressed concern on Friday over reports that Israeli soldiers fired live ammunition against Palestinian protesters at the border of the Gaza Strip.

All measures to defend Israeli security interests needed to be "proportionate", Reiner Breul, a spokesperson for the German Foreign Office, told press in Berlin.

Breul emphasized that "protesters cannot be fired upon", whilst noting that Palestinians must also refrain from abusing the right to freedom of expression and peaceful demonstrations.

According to the spokesperson, the German government had seen "credible reports" about a high number of injured protesters at hospitals in Gaza city. "The high number of victims of gunshot wounds can hardly be reconciled with a measured application of the right to defense," Breul argued.

As a consequence of the events, Berlin expected a thorough investigation of the incident. At least 18 Palestinians have been killed and more than 1,000 wounded since the beginning of protests on March 30 at the border between Gaza and Israel.

Further demonstrations were announced for Friday which prompted Israeli armed forces to warn that they would react with force. The United Nations (UN) High Commissioner for Human Rights Zeid Ra'ad Al Hussein has urged Israel to prevent excessive violence on behalf of its armed forces.