Germany's trade surplus grew slightly in August compared with the previous month, official data showed on Tuesday, with no sign complaints from abroad are sapping the export strength of Europe's powerhouse.

Exports outweighed imports by 21.6 billion euros ($25.5 billion) in August, slightly more than in July, federal statistics authority Destatis said in seasonally-adjusted figures.

Still in adjusted terms, Germany sold 3.1 percent more goods abroad than in July, at 108.4 billion euros.

Imports grew more slowly, adding 1.2 percent to reach 86.8 billion.

Germany registered a trade surplus of around 250 billion euros in 2016, a figure that has become a bone of contention with allies and trade partners.

They complain the country fails to buy enough from abroad to share the fruits of its economic success -- so far to no avail.

"Despite the summer lull, 2017 should be the best year for German exports since 2010," forecast ING Diba bank economist Carsten Brzeski.

Outside factors are "the biggest risks for the German economy and the export sector," he added, pointing to global flashpoints like North Korea and chances of an economic slowdown in the United States or Britain -- two of Germany's biggest customers.