Volodymyr Groysman said he stayed up until "2:30 in the morning trying to enter the (internet) system".
Ukraine's prime minister said on Wednesday he had completed an online declaration of his income required to unlock the next tranche of an IMF loan -- despite the filing website malfunctioning late into the night.
Volodymyr Groysman said he stayed up until "2:30 in the morning trying to enter the (internet) system".
"It was impossible," he added in a statement released by his office.
Groysman's frustration underscores the difficulties Ukraine faces as it races against the clock to make itself more transparent and shed the image of widespread corruption that brought down one pro-Western government in April.
The electronic declaration forms must be filed by all officials and made available to journalists and curious Ukrainians for viewing on a website by next Tuesday.
The measure itself was passed after months of foot-dragging by lawmakers alarmed by the law.
But the measure is a key requirement for the disbursement of a $1 billion (920 million euro) loan that Ukraine received in September from the International Monetary Fund after a delay of more than a year.
The prosecutor general's office took the unusual step of blaming the glitch on inquisitive media whose interest in officials' income was overwhelming the site.
The internet "has been occupied and brought down by reporters," prosecutor's office spokeswoman Larysa Sargan wrote on Facebook.
Sargan later added that her remarks were meant to be interpreted as ironic.
The former Soviet republic is trying to claw its way back from crises that include a 30-month-long pro-Russian separatist insurgency in its industrial east and a devastating two-year recession that only ended at the start of the year.
But Western allies who supported Kiev's February 2014 revolution that brought down its detested Russian-backed president want Ukraine to take on more responsibility for tackling the graft raging through all levels of government.
Transparency International ranked Ukraine as the world's 130th most corrupt state out of 168 countries and territories on its list.
The organisation's Ukrainian branch noted last week "that almost none of the top officials have filed their income declarations yet".
Ukraine hopes to receive its next IMF tranche payment in December.