Azerbaijan was searching on Sunday for 30 missing oil workers after a storm caused their offshore oil rig to catch fire.
Two people have been confirmed dead since the accident on Friday, one of whom was found early Sunday, said a joint statement by state energy firm SOCAR and the emergency ministry.
Rescue workers managed to evacuate 33 people from the rig, where they had been hanging onto lifeboats 10 metres above the stormy waters of the Caspian Sea.
A source in the administration of President Ilham Aliyev told AFP news agency that Sunday was designated a day of national mourning.
"Flags will be at half-mast in Azerbaijan as well as its diplomatic missions in other countries," Aliyev said. "Entertainment events and television concert programmes have been cancelled."
There were indications that safety regulations had been violated, a judicial spokesman said in the capital Baku.
The oil field is located about 120km east of Baku.