"Danger exists for other regions," Emergency Minister Viktor Baloga told parliament during a debate on endorsing a state of emergency imposed by President Viktor Yushchenko in five villages in Crimea. More than 2,500 birds died at the weekend.
"It is better to adopt tougher measures now rather than tomorrow. Otherwise, we will have problems throughout Ukraine."
Ukraine reported its first outbreak of the disease at the weekend. But residents said signs of the illness had been detected since September, with no measures taken.
Outbreaks of a deadly form of avian flu have been detected in birds in Romania on Ukraine's western border and in Russia to the east.
Baloga said Emergency Ministry troops would complete a cull of domestic poultry in affected areas by Wednesday night. The ministry said its staff had seized more than 22,000 birds in house-to-house checks of villages sealed off by exclusion zones.
Authorities have sent samples of bird tissue to specialized laboratories in Britain and elsewhere to determine whether the strain is the deadly H5N1 detected in Romania and Russia.
H5N1 is endemic in poultry in parts of Asia where it has killed almost 70 people. Experts fear the virus could mutate into a form which can be transmitted easily from person to person, risking a pandemic in which millions could die.
As required by the constitution, parliament approved the president's decree on emergency rule, invoked for the first time since Ukraine split from the Soviet Union 14 years ago.
But a motion approved by 291 members in the 450-seat house also demanded the president submit details of the measures, how long they would remain in place and to what extent they would affect Ukrainians' rights.
Some opposition members had argued that Yushchenko's weekend decree, which set no time limit on the measures, could disrupt a March 2006 parliamentary election as campaigning gets under way.
The president toured affected areas on Monday and expressed frustration at lack of action. He ordered the dismissal of Ukraine's chief veterinarian.
Officials from the emergency, agriculture and health ministries declared the situation under control, with no new cases. But they said the state of emergency was vital to contain the disease.
While workers incinerated domestic fowl in napalm left over from the Soviet era, Interior Ministry troops stood guard at checkpoints 3 km (two miles) outside the villages, restricting movement and barring any transport of meat.
Residents received compensation for each head of confiscated fowl, payments starting at $3 for a chicken and ranging to about $18 for a turkey. Doctors proceeded with mass vaccinations for residents against seasonal flu.
Ukraine's Health Ministry urged consumers not to panic and said it was safe to eat poultry produced by industrial farms.