Chilean bank BancoEstado closed all of its branches on Monday in response to a ransomware attack over the weekend.

On Sunday, the bank confirmed that it had "detected malicious software" in its operating systems but stressed that customer funds have not been affected.

According to ZDNet, citing sources, the bank's internal network was infected with the REvil ransomware after an employee opened a malicious Office document.

The ransomware appears to have encrypted most internal servers and employee workstations, prompting the decision to keep branches closed on Monday.

However, the hackers have not gained access to BancoEstado's ATMs, app and website, which are all working.