Kiev: Construction has started on a gigantic steel-arch to cover the remnants of the Chernobyl reactor on the 26th anniversary of the world's worst nuclear accident.

Ukrainians on Thursday are marking the anniversary of the nuclear power plant's explosion.

President Viktor Yanukovych is set to inaugurate the initial assembly of the arch over the reactor - big enough to house the Statue of Liberty in New York.

When the arch is completed in 2015, the delicate and dangerous job of dismantling the reactor and cleaning vast amounts of radioactive waste can begin.

The April 26, 1986 explosion spewed a cloud of radiation over much of the Northern Hemisphere, forcing hundreds of thousands of people from their homes in heavily hit areas of Ukraine, Belarus and western Russia.