A top Ukrainian rebel leader said on Sunday that the pro-Russian fighters will guarantee the safety of international monitors at the Malaysian jet's crash site if Kiev agrees to a truce.

"We declare that we will guarantee the safety of international experts on the scene as soon as Kiev concludes a ceasefire agreement," the self-proclaimed Donetsk People's Republic's deputy premier Andrei Purgin said in a statement.

He urged Kiev to "immediately conclude such an agreement" with the rebels.

Failure to do so would give the impression that the government is made up of "dangerous lunatics, bloodthirsty maniacs (who are) dangerous not only for the residents of Donbass but also for the world community", Purgin warned.

Purgin's statement came as the international community piled pressure on Russia to get the Moscow-backed rebels to grant investigators full access to the crash site of the Malaysian MH17 jet.