President Poroshenko of Ukraine has warned he may bring in martial law because of increased tension in the east with pro-Russian separatists.
He also said the conflict could escalate and even bring a full Russian invasion.
Earlier the Ukrainian military reported that three servicemen had been killed and six wounded in fighting over the previous 24 hours.
The president’s comments came at a ceremony in the western city of Brody to honour dead Ukrainian pilots.
He didn’t spell out what martial law might mean or where it might take effect.
“If the situation escalates, mobilisation and martial law will be introduced by my decree,” he said.
Separatist officials have accused Kyiv’s forces of firing at rebel-held territory, and of deploying heavy weapons that were supposed to have been withdrawn.
Monitoring the 18-month-old ceasefire agreement, the Organisation for Security and Cooperation in Europe (OSCE) has reported an increase in the number of violations and explosions in eastern regions, while describing the administrative boundary line with Crimea as calm.