During the Belarus people’s assembly, Alexander Lukashenko said that the West forgot promises not to push NATO to the East.
[The expulsion of European diplomats] was decided as soon as it was identified that they participated in illegal rallies. Afterwards, “rumours” began to appear that the diplomats were doing their job, their professional duties, [and] were arrested illegally, accused of something they did not commit – participate in the illegal rallies.
Recurring pro-Kremlin disinformation narrative concerning the ongoing protests in support of jailed opposition activist Alexei Navalny.
The European Union has condemned the expulsion of three European diplomats and rejected accusations that conducted any activities incompatible with their diplomatic status. The diplomats were fulfilling their duties of monitoring the street protests in Russia. According to the 1961 Vienna Convention on Diplomatic Relations, these duties include "[a]scertaining by all lawful means conditions and developments in the receiving State, and reporting thereon to the Government of the sending State" (Article 3(d)).
Furthermore, the protests currently taking place in Russia are not "illegal," given that the universal right of peaceful assembly is guaranteed by the Russian Constitution (Art. 31). A term of "unsanctioned" rallies is usually invoked by the pro-Kremlin actors as a pretext to deny Russian citizens their constitutional rights, and which is incompatible with both domestic legislation and international norms. See here for further debunking.
See also similar disinformation claims that Diplomats from EU took part in unsanctioned rallies and that Russia was forced to expel EU diplomats who participated in illegal protests.