MINSK: Belarusian strongman Alexander Lukashenko is convening hundreds of loyal delegates at a people's assembly on Thursday to unveil promised reforms, in a display the embattled opposition has dismissed as political theatre.

Europe's longest-serving leader is expected to roll out proposals to placate demonstrators who flooded streets across the ex-Soviet country last year to protest against his claim to a sixth presidential term following an election in August.

The authoritarian ruler made promises in November to change the constitution to calm the protests just weeks after he was shown at a rally brandishing a Kalashnikov assault rifle and referring to protesters as rats.

But opposition protests have subsided in recent weeks, and in the days leading up to the assembly, Lukashenko made no mention of the promised constitutional changes.

On the eve of the assembly he instead highlighted a state-initiated survey that he said will determine the outcomes of the gathering, which draws around 2,700 hand-picked representatives from mostly state-backed sectors.

"It is very difficult at the All-Belarusian People's Assembly to plan something without knowing the deep sentiments in society," Lukashenko was cited by his press service as saying.

The Nexta Telegram channel, which mobilised and coordinated demonstrators over the months of rallies, called for fresh demonstrations on Thursday and Friday when the assembly will be in session.

"This is a gathering of unfortunate Lukashenko supporters who were rounded up for one purpose -- to amuse the pride of one person," Nexta wrote, encouraging residents of Minsk to take to the streets.

Belarus police, however, promised to "suppress" any illegal activities and warned of potential road closures in the capital, officially due to expected heavy snowfall.