Dortmund -- Erling Haaland promised "there is a lot more to come" after taking his tally at Borussia Dortmund to seven goals in three matches during the 5-0 Bundesliga win against Union Berlin on Saturday.

Haaland, 19, joined from FC Salzburg in January and has played a key role as Dortmund have revived their Bundesliga title hopes by scoring five goals in three consecutive matches.

"I think it's a mix of hard work and good teammates around me," Haaland told reporters after making his first start for BVB. "My teammates are so good. Then it's getting easy for me. I am enjoying my time so far and there's a lot more to come."

Having come off the bench as a substitute in the previous two games, Haaland had already contributed five goals of Dortmund's 10 as they beat Augsburg 5-3 and Cologne 5-1. Against Union Berlin he needed only 18 minutes to score from a Julian Brandt cross.

He later added a second after another Brandt assist and also won a penalty for Dortmund during a crucial phase of the match midway through the second half. Club captain Marco Reus converted to make it 3-0.

"I didn't think about [scoring] so many goals, but now it's seven and I am enjoying it," he added.

Dortmund officials and players said they were pleased with the Norwegian's arrival at the Westfalenstadion.

"You can't imagine a better start," Dortmund sporting director Michael Zorc, who beat Manchester United and Juventus to Haaland's signature this winter, said.

"His job is to score goals. You can see that with every fibre of his body," he added and, when asked to compare him with other great attackers of the game, Zorc said: "He's only 19 years old. We don't make any comparisons. It makes no sense. Let him just play football and then he will score."

Former Dortmund defender Neven Subotic was willing to make comparisons and likened Haaland to Bundesliga legend Robert Lewandowski and Arsenal forward Pierre-Emerick Aubameyang.

"He reminds me of Lewandowski," Subotic, who now plays for Union Berlin, said. "He needs half a chance to score a goal and he's proven it again today. He can score goals from difficult situations.

"It's a mix of Lewandowksi and Aubameyang," he added. "That's a huge compliment for him."

But the headlines not only belonged to Haaland. On Saturday, England international Jadon Sancho set a new league record with the opening goal of the afternoon.

"We have quite a few 19-year olds who are incredible. I just saw the stats. Jadon is the first player under 20-years-old to reach 25 goals in Bundesliga. That's unbelievable," Zorc said. "But maybe Erling will get there too."