Nepal government’s main server continues to face cyberattacks aimed at shutting it down even though a large number of official websites were restored after Saturday’s intrusion.

The cyberattacks that resulted in disruptions of hundreds of government websites across the country on Saturday had also hit international travel due to the shutdown of the immigration server.

“Server system failure affected the operation of flights throughout the day on Saturday,” said Prem Nath Thakur, general manager at the Tribhuvan International Airport. “We managed to release a few planes manually,” he said, adding that flights of Nepal Airlines, Air India and Indigo Airlines were delayed by over an hour.

Officials said it was distributed denial of service (DDoS) attacks which are a subclass of denial of service (DoS) attacks. A DDoS attack involves multiple connected online devices, collectively known as a botnet, which are used to overwhelm a target website with fake traffic.

“We have been able to reduce the size of traffic, enabling the reopening of most government websites,” said Ramesh Prasad Pokharel, assistant director at the National Information Technology Centre (NITC) under the Ministry of Communication and Information Technology. “But attacks on our main server continued even on Sunday.”