SEOUL, South Korea — Two of South Korea's largest megachurches are confronting suspected cyberattacks that may have exposed the personal information of nearly a million church members, according to reports released this week.

The cybersecurity firm Oasis Security announced it had discovered attack records and account information connected to Yoido Full Gospel Church — believed to be the largest single church congregation in the world — and SaRang Church on a server located outside South Korea, the Christian Post reported Saturday.

The initial analysis indicates that data connected to as many as 850,000 members of Yoido Full Gospel Church could be compromised, according to Reuters. The church said it was informed of the breach by the Korea Internet & Security Agency on Tuesday.

Yoido confirmed the exposed data includes members' names and birth dates. Some records also contained phone numbers, addresses, and national identification numbers, which were found in a log of edits to membership entries. The church reported 2,629 changes to resident registration numbers, 3,964 changes to phone numbers, and 7,202 changes to addresses.

"I feel a deep sense of responsibility for causing concern among our members as a result of this incident, and I sincerely apologize," Senior Pastor Lee Young-hoon said in a statement, according to The Korea Times.

Since the breach came to light, the church has blocked outside access to its systems, changed its server passwords, and begun notifying people who may be affected. Yoido also plans to install a new firewall and hire security firms to look for other vulnerabilities.

Meanwhile, SaRang Church, a Presbyterian congregation in southern Seoul, is dealing with a suspected attack of its own involving the files of about 89,000 congregants and 286 staff members, including the senior pastor. Attack logs suggest the SaRang data was taken in August. The church has formed an emergency response team and reported the breach to authorities.

Both churches say they are still investigating, and neither has yet determined how the attackers gained access to its systems. Records from the attacks suggest the hackers may have used artificial intelligence tools — Oasis noted the presence of automated "sub-agents" in the attack logs — though the exact role of AI remains unclear.

The church breaches follow a string of recent hacks of South Korean commercial banks that exposed customers' personal information, including one reported incident at Shinhan Bank involving about 25,000 customers. President Lee Jae Myung said this week that some of those incidents showed signs of AI involvement.

Under South Korea's Personal Information Protection Act, organizations are required to notify people when their personal data has been leaked — a step both churches say they are taking as their investigations continue.