Germany coach Joachim Loew was left counting the cost of Friday's 6-1 thrashing of Armenia which threatens to rule Marco Reus out of the World Cup with injury.

The 25-year-old was rushed to hospital having being helped off in obvious distress after twisting his left ankle just before the half-time break in a challenge.

"We need to see the results of the MRT scan, of course a lot of things go through your head, but I hope it's not quite as bad as it seems," said Loew.

"You could see the foot was swollen and I hope it's not a ligament (injury)."

Reus' injury put a dampener on an impressive display as goals by Lukas Podolski, Benedikt Hoewedes and Mario Goetze, who scored twice, floored minnows Armenia, who had a penalty converted by Henrikh Mkhitaryan.

Replacement Miroslav Klose, who turns 36 on Monday, made history when he headed home their fourth to become Germany's all-time top scorer.

Klose netted his 69th goal for Germany on his 132nd appearance to finally break Gerd Mueller's previous mark of 68 goals in 62 matches for West Germany.

Loew had said he wanted to leave Germany for Brazil with a smile and his side upped the pace with five goals in 17 second-half minutes.

The Germany boss said the Brazilian climate will be a factor when his side kick-off their Group G campaign against Portugal on June 16, but is something they are planning for.

"There are lots of things which need to work at a big tournament," said Loew.

"When you come from Europe (to Brazil), you can't assume to be able to play the same type of football, which we can here.

"I have experienced the temperatures and humidity (in Brazil), you can't expect to go flat out for 90 minutes.

"So efficiency in taking your chances is an important topic for us."

Despite Reus' injury, there were several plus points for Loew.

Both captain Philipp Lahm and his deputy Bastian Schweinsteiger played after enforced injury breaks, while Arsenal star Lukas Podolski provided two assists and a goal in an impressive second-half display for Reus on the left wing.

"If you look at the statistics, we had lots of goal chances and we need knock them in earlier," said the 29-year-old Podolski, who scored his 47th goal on his 114th appearance.

"We showed what we can do in the second-half, now we have to prepare well for Portugal, who are a tough team and will be a different calibre than today.

"It's very important to win your first game."