A second episode of uncontrolled shaking sparked concerns about the wellbeing of Angela Merkel.

The German government insisted Friday that Chancellor Angela Merkel was in robust health, after a second episode of uncontrolled shaking sparked concerns about the wellbeing of the EU's longest-serving leader.

Asked about how Merkel, who is in Japan for a G20 summit, was faring after her second trembling spell in as many weeks, government spokeswoman Martina Fietz said she was fine.

"The images you can see from Osaka show that the chancellor is very active and healthy -- doing her job and keeping her planned appointments," Fietz told reporters.

The long-serving leader, who turns 65 next month, sparked renewed fears for her health Thursday when she began to tremble at a ceremony with the German president at his Berlin palace.

A previous, more severe bout of uncontrollable shaking last week was blamed on dehydration at an outdoor event on a hot summer's day.

Officials sought to play down the fears over her health.

Her spokesman Steffen Seibert said she would not cancel any of her engagements in the coming days, which promise to be gruelling.

Merkel, who has been in power for nearly 14 years, is to participate in the two-day G20 gathering and is holding a number of bilateral meetings including with US President Donald Trump.

She flies from Osaka straight to a crunch EU summit on Sunday where leaders will seek to break a post-election deadlock on who will lead the bloc's institutions.

Merkel has said she will leave politics at the end of her term in 2021.