By Sarah Rainsford
BBC News, Minsk
Nineteen years after the Chernobyl nuclear disaster in Ukraine, Belarus is still suffering the consequences.
Fallout from Chernobyl displaced thousands in Belarus
In Minsk, opposition activists will join residents of the contaminated regions in a march to mark the anniversary.
President Alexander Lukashenko is marking the Chernobyl anniversary according to tradition.
He is heading to the south of Belarus, to one of the areas worst affected by radiation from the Ukrainian plant.
Belarus suffered the worst of the radioactive fall-out, but the toxic cloud also spread across a large swathe of Europe.
State television has been trailing the trip as yet another sign that life in the Chernobyl disaster zone is returning to normal.
The authorities here are promoting the development of the area, investing in agriculture in particular.
As more than 1.5 million people still live there, that is largely a product of necessity.
But opposition activists and local scientists are concerned about the safety of such a policy.
They point to high levels of child sickness in the region as proof it is still far from safe.
As the president demonstrates the opposite, they will use a protest meeting in Minsk to deliver a petition to his office.
They are calling for an honest approach.
They will also protest against new regulations that make it more difficult for children from the contaminated zones to travel abroad.
Last year President Lukashenko declared such trips were corrupting Belarussian children by exposing them to capitalism.