Lukashenko's statement stressed they were "non-strategic" nuclear weapons, so not longer-range and higher-yield bombs.
Speaking in Moscow, Lukashenko said that the movement of the weapons was already underway, after Russian President Vladimir Putin signed the decree. But he did not make it clear whether any had arrived in Belarus.
The agreement allows Moscow to store warheads at a special facility in Belarus.
Russia would maintain control of the weapons, as per the deal, which formalizes an earlier agreement between the two state leaders and allies.
Previously in March, Putin announced the intention to deploy tactical nuclear weapons in Belarus.
Berlin slams planned nuke deployment
The German government has strongly condemned Lukashenko's announcement that Russian nuclear weapons were being moved to his country.
"The transfer of Russian tactical nuclear weapons to Belarus, as claimed by Lukashenko, is another transparent attempt at nuclear intimidation by Russia," deputy government spokesman Wolfgang Büchner said.
"We firmly reject this."
The European Union also criticized the agreement between Russia and Belarus. "This is a step which will lead to further extremely dangerous escalation," EU foreign policy chief Josep Borrell said in a statement, adding that the decision contravened multiple international agreements.
"We call on Russia to abide by these commitments," he said.
What do we know about the deal?
"Deployment of nonstrategic nuclear weapons is an effective response to the aggressive policy of countries unfriendly to us," the Associated Press news agency cited Belarusian Defense Minister Viktor Khrenin as saying in Minsk during a meeting with his Russian counterpart, Sergei Shoigu.
"In the context of an extremely sharp escalation of threats on the western borders of Russia and Belarus, a decision was made to take countermeasures in the military-nuclear sphere," Shoigu added, according to AP.
Meanwhile, exiled Belarusian opposition leader Sviatlana Tsikhanouskaya warned that Putin's plan to station nuclear weapons in Belarus would "ensure Russia's control over Belarus for years to come."
"This will further jeopardize the security of Ukraine and all of Europe," he told AP.
Last year, Minsk allowed Moscow to use its territory for launching attacks on Ukraine. Belarus borders Ukraine to the north and entering from Belarus created a far wider front than just using the Russian frontier to Ukraine's east, also opening a front closer to the capital Kyiv.
rmt/msh (AP, Reuters)