Seoul, South Korea (CNN) -- South Korean police said Wednesday they are investigating a computer outage that has struck systems at leading television broadcasters and banks, prompting the military to step up its cyber alert level amid concerns about North Korea.
One television station, YTN, reported that 500 of its computers had been disabled by the outage. Another, KBS, said that its internal networks had been "paralyzed," but that the problem didn't prevent it from broadcasting live.
A third broadcaster, MBC, was also reportedly experiencing problems.
Customers of Shinhan Bank are unable to log into the lender's website at the moment, the company said in a statement.
A second lender, Nonghyup Bank, said that it had disconnected some of its computers after they were infected with a virus. The bank said its main server was still functioning and able to carry out Internet transactions.
Police didn't immediately provide a reason for the server problems.
The South Korean defense ministry said it had upgraded its information operations condition, or INFOCON, one notch to level 3 in response to the outages. Level 1 is the highest on the scale, which gauges the perceived likelihood of a network attack.
The ministry said it couldn't say whether North Korea, which has made a number of recent threats against South Korea and the United States, was behind the computer problems.
The defense ministry said it had already increased the alert level last month in response to North Korean threats.
The South Korean government has set up a cyber crisis management team, bringing together civilian, government and military officials, said Kim Haing, a spokeswoman for the South Korean president's office.
NEW: The South Korean government has set up a cyber crisis team
NEW: A second bank reports computer problems
The South Korean defense ministry upgrades its information alert level
Police are investigating, but have not given a reason for the outage