The North's official KCNA news agency said the exercises were a "provocation" and a rehearsal for an invasion.
It also warned the US over the fate of the historic summit between Kim Jong-un and US President Donald Trump that is scheduled for 12 June in Singapore.
In March, Mr Trump stunned the world by accepting an invitation to meet Mr Kim.
"We will both try to make it a very special moment for World Peace!" the US leader later tweeted.
The US state department said it was continuing to prepare for the Trump-Kim summit and that it was not aware of any changes in the North Korean position.