NORTH KOREA/SOUTH KOREA/GERMANY (REUTERS) - Just days before Donald Trump's visit to Asia, tensions on the Korean peninsula are once again rising fast.

Seoul, launching a live-fire exercise with a range of missiles on Thursday (Nov 3), as US bombers fly through Korean skies, accompanied by fighter jets from South Korea and Japan.

And according to experts, the North might be planning some activity of its own.

South Korea's spy agency says its spotted movement at one of Kim Jong Un's research facilities, fueling speculation that the North could launch another missile in the near future, possibly during Trump's visit to Seoul.

North Korea has not tested any missiles since its latest and largest launch in September, making these past few months the longest lull this year.

South Korean intelligence says the nuclear site may have been damaged during that test, which triggered aftershocks.

But Seoul expects Pyongyang will detonate more devices as it continues its efforts to attach a nuclear warhead to a ballistic rocket.

Trump will hold talks in five Asian countries in the coming and North Korea will be a major focus.

He'll be looking to increase international support for even more sanctions as Washington says it's "running out of time" to deal with the regime.