BERLIN, Feb. 23 (Xinhua) -- German stocks saw small gains at the start of trading Tuesday, with the benchmark DAX index growing by 34.94 points, or 0.25 percent, opening at 13,984.98 points.

The biggest winner among Germany's 30 largest listed companies at the start of trading was plastic specialist Covestro, increasing by 2.36 percent, followed by Deutsche Bank with 1.99 percent and aircraft engine manufacturer MTU Aero Engines with 1.33 percent.

On Tuesday, Covestro announced a "strong end to an exceptional year in 2020" although full year sales fell by 13.7 percent to 10.7 billion euros (13 billion U.S. dollars). EBITDA declined by 8.2 percent to 1.5 billion euros as expected as the company implemented "extensive cost-saving measures."

Shares of HeidelbergCement fell by 1.95 percent. The German building materials company was the biggest loser at the start of trading Tuesday after announcing that full year revenues declined by 6.6 percent to 17.6 billion euros due to the decline in sales volumes.

On Tuesday, dialysis specialist Fresenius announced that full year 2020 sales grew by 2 percent to 36.3 billion euros while EBIT slightly declined by 2 percent to 4.6 billion euros. Despite upcoming challenges due to the pandemic, Fresenius expects a "healthy business development" in 2021.

The yield on German ten-year bonds went up 0.033 percentage points to minus 0.314 percent and the euro was trading almost unchanged at 1.2161 dollars, increasing by 0.01 percent on Tuesday morning.