Russian forces continued to bombard towns in Ukraine on Christmas Day, despite Russian President Vladimir Putin's statement that he was open to negotiations. The attacks took place in the Kupiansk district of the Kharkiv region, where more than 10 rocket attacks were launched, and along the Kupiansk-Lyman frontline, where more than 25 towns were shelled. The attacks came as a response to Ukraine's decision to impose martial law in parts of the country in response to Russia's recent aggression. The United States has dismissed Putin's offer of negotiations as posturing, citing the continued Russian attacks. Meanwhile, Ukrainian President Petro Poroshenko has called on the international community to support Ukraine in its fight against Russian aggression. "We will not cede an inch of Ukrainian land to anyone," Poroshenko said in a statement. "We will defend our sovereignty and territorial integrity with all means available to us." The Ukrainian government has also called on the United Nations to take action against the Russian aggression. The escalating tensions between Ukraine and Russia have raised fears of a full-scale war, and have put a strain on relations between the two countries. The United States and its allies have condemned the Russian attacks and urged both sides to de-escalate the situation.