Ukraine's parliament approved a presidential decree on Tuesday to call up more military reserves and men under 50 to fight rebels in eastern Ukraine and defend the border against a concentration of troops in Russia.
Some 45 days after the latest call-up of additional reserves, which has now expired, Kiev repeated the decree to "declare and conduct partial mobilization" to ensure the ranks of what Ukraine calls its "anti-terrorist operation" are filled.
After the vote, brief scuffles broke out between nationalist politicians and members of the party that was led by the former president, Viktor Yanukovych, who was overthrown in February.
Ukrainian troops have forced pro-Russian rebels back to their two main strongholds, the cities of Donetsk and Luhansk, slowly taking villages and city suburbs around them.
The army is under orders not to use air strikes and artillery in the cities, complicating operations to restore control despite Kiev's accusations that the rebels were responsible for the shooting down of a Malaysian airliner. The separatists deny the accusations.
"Russia continues its policy of escalating its armed confrontation," Ukraine's top security official, Andriy Paruby, told parliament before 232 deputies in the 450-seat parliament voted in favor of the decree.
Reiterating accusations leveled by Ukrainian officials against Moscow, he said: "Over the last week, close to the Ukrainian border, there has been a regrouping and build-up of forces of the Russian Federation."
Paruby put the numbers close to the border at 41,000 and said they were equipped with 150 tanks, 400 armored vehicles and 500 other weapon systems.
He said some of the new Ukrainian recruits would join or support combat units and some of the others would support units to help defend the border.
Russia withdrew most of the 40,000 troops it had close to the border earlier this year, reducing them to fewer than 1,000 by mid-June. But since then, it has been building up its forces again, a NATO military officer said this month.
Paruby accused Russia of continuing to supply the rebels, who say they are fighting to win independence from Kiev for the Donbass coal mining region.
"Such actions are classified as aggression against our state," he said.