The outages come amid tension between Ukraine and Russia.
Ukraine's Ministry of Defense website suffered from what appeared to be a distributed denial of service attack Tuesday, according to the government's Facebook account. DDoS attacks cripple sites by overwhelming them with a flood of requests to serve up web pages.
The military's website remained unavailable as of 12 p.m. PT Tuesday, with the Ukrainian military's Facebook account saying work is currently underway to restore regular functioning to the online portal.
The nation's largest commercial bank, PrivatBank, has also been subjected to a "massive DDoS attack" for the past few hours, according to the Ukraine Center for Strategic Communications. There's no threat to customer funds stored at the bank, it said, though the attack is preventing customers from accessing the Privat24 application and viewing their balances.
Online banking with Oschadbank is also down, the Center for Strategic Communications said, as reported earlier by Vice.
The Tuesday campaign has yet to be attributed to anyone, but it comes after Russia is believed to have mounted multiple cyberattacks on Ukraine as part of efforts that security experts say are designed to destabilize the country's government and economy.
Russia, which has amassed more than 100,000 troops on Ukraine's borders, pulled back some personnel, according to reports on Tuesday. Russia has repeatedly denied any plans to attack Ukraine.