Bitcoin dropped below $100,000 for the first time since May and Ether also fell sharply after US bombers attacked Iran's nuclear sites, prompting risk aversion in digital-asset markets.
Bitcoin fell by 3.8% to $98,904, while Ether dropped up to 10% to about $2,157, its lowest level since May 8.
Geopolitical tensions are causing concern in the markets, with focus shifting to oil prices when traditional markets reopen.
President Trump's announcement about the US strikes on Iran's nuclear sites led to market uncertainty and a selloff, affecting cryptocurrency investments.
Over $1 billion in liquidation of crypto bets occurred over the last 24 hours, with significant closures in long and short positions.
Bitcoin is seen as a potential indicator for market recovery during times of geopolitical unrest.