The weapons are expected to be used in response to North Korea's decision to send thousands of troops to Russia in support of Russian President Vladimir Putin's invasion of Ukraine, according to one of the sources.
Volodymyr Zelenskyy has spoken after a long-awaited decision came from Washington giving permission for Ukraine to use US-supplied long-range missiles to strike targets deeper inside Russia.
But despite Zelenskyy pleading such permission for weeks, his response in his nightly video address was notably muted.
"Today, much is being said in the media about us receiving permission for the relevant actions. But strikes are not made with words. Such things are not announced. The missiles will speak for themselves," he said.
Zelenskyy's comments come after reports emerged that President Joe Biden had authorised the use of US weaponry by Ukraine to strike inside Russia in a major US policy shift in his final weeks in the White House.
The weapons are expected to be used in response to North Korea's decision to send thousands of troops to Russia in support of Russian President Vladimir Putin's invasion of Ukraine, according to one of the sources.
Zelenskyy also spoke about Russia's massive drone and missile attack on Ukraine on Sunday, described by officials as one of the largest ever that targeted energy infrastructure and killed civilians.
That attack came as fears mount about Moscow's intentions to devastate Ukraine's power generation capacity ahead of the cold winter.
Russia reportedly launched a total of 120 missiles and 90 drones in a large-scale attack across Ukraine.
