Ex-Chelsea striker Salomon Kalou says criticism from his Hertha Berlin coach has seen the Ivory Coast star rediscover his goal-scoring touch in Germany's top flight.

The 30-year-old, who played for Premier League side Chelsea from 2006 until 2012, arrived in the German capital at the start of last season, but scored just six goals in his first Bundesliga campaign, which drew criticism from Berlin coach Pal Dardai.

This season he has already netted seven goals in 11 league games, including a hat-trick in the 3-1 win at Hanover 96 ten days ago, and Kalou says Dardai's harsh words have helped him score to push Hertha up to fourth in the Bundesliga.

"He's a hard person, because he is honest," Kalou told German magazine Kicker.

"You need to tolerate hearing the truth, he tells you exactly what you lack and when there is only harmony, you don't achieve anything in football.

"I now know how the Bundesliga works and for the first time, I took full part in all the pre-season training this summer -- that was the key."

Kalou was part of the Ivory Coast squad which won the 2015 Africa Cup of Nations, converting a spot-kick when his side won February's final 9-8 in a penalty shoot-out against Ghana following a goalless draw.

But when last season ended in May, Dardai said he needed to see "more aggression, more fire" from his Ivory Coast star and Kalou admits the tough talk had the desired effect.

"He has the right to do, he's the boss and as players we should want to improve ourselves," said Kalou.

"Pal Dardai managed it, he pushes me to the limit."