DONETSK, Ukraine — Pro-Russian rebels in eastern Ukraine on Friday rejected a previously signed peace deal and announced a new multipronged offensive against Ukrainian government troops, defying diplomatic efforts to end the spiraling crisis.The main separatist leader in the Donetsk region said the insurgents won’t engage in further cease-fire talks, and another rebel went even further saying they will not abide by a peace deal signed in September. Separatist leader Alexander Zakharchenko said rebel fighters launched the new offensive to gain more territory and forestall a Ukrainian attack. He declared they will push the government troops to the border of the Donetsk region and possibly even further.“Attempts to talk about a cease-fire will no longer be undertaken by our side,” Zakharchenko said. The peace deal signed in September in the Belarusian capital of Minsk envisaged a cease-fire and a pullout of heavy weapons from a division line in eastern Ukraine. It has been repeatedly violated by both sides, and there has been a surge in fighting in the last few weeks that swelled the death toll to nearly 5,100 since April, according to the United Nations’ human rights agency.