Russian citizens will no longer be able to travel to Ukraine using their internal passports, Ukrainian Prime Minister Arseniy Yatsenyuk has announced.
The change, announced on Tuesday and to take effect on March 1, discontinues a preferential travel regime between Russia and Ukraine that allowed citizens of the countries to cross each other's borders without an international travel document.
Russians carry two passports, one for identification and travel uses inside of the country, and an international passport recognised abroad.
Yatsenyuk said the change was the result of a request from Russian President Vladimir Putin.
"I remember Vladimir Putin asked to move on crossing over the state border with foreign passports only. Then what can we do? We heard his request," Yatsenyuk told a ministers' meeting.
"Now Russian citizens must - as Vladimir Putin asked - use foreign passports only. It will give us the ability to strengthen control substantially, and it will give us the ability to substantially secure the national security interests of Ukraine," he added.
The move comes as fighting between Ukrainian troops and pro-Russian separatists continues in eastern Ukraine. More than 5,000 people have been killed in fighting and hundreds of thousands have been forced to flee.