Ukraine steps up defences, citing growing Russian aggression

Ukraine's parliament voted on Thursday to refresh its front-line forces and resume partial conscription after a top security official warned that Russian forces backing separatist rebels had sharply increased military activity in the east.

"Russian aggression is continuing. There has been a significant surge in the intensity of firing," Oleksander Turchynov, secretary of the national defence council, told parliament, adding that 8,500 Russian regular forces were now deployed in eastern Ukraine.

Two Ukrainian soldiers were killed and four wounded on Wednesday when Ukrainian positions were fired on 129 times, which Turchynov said was a record for this year so far.

The warning of increased military activity by Russian forces also followed the shelling of a passenger bus on Tuesday at an army checkpoint in which 13 people were killed. Kyiv blamed the separatists for the attack but they denied responsibility.

Despite what the West and Kyiv say is incontrovertible evidence, Moscow denies it has any troops in the east of Ukraine where pro-Russian separatists are fighting government forces in a conflict in which more than 4,700 people have been killed.

Ukraine's parliament supported a decree of President Petro Poroshenko to swap out long-serving troops at the front and to bring in veterans from the reserve as well as resume partial conscription.

Ukraine scrapped compulsory military call-up in 2013 before the ousting of a pro-Moscow president, Viktor Yanukovich, which sparked the confrontation with Russia.

"There is an urgent need to strengthen the combat and mobilization readiness of our forces and other military forces up to a level which guarantees an adequate reaction to threats to national security from continuing Russian aggression," Turchynov said.