MOSCOW, Sha'ban 22, 1435, Jun 20, 2014, SPA -- Russia described Ukraine's ceasefire announcement on Friday as an ultimatum to pro-Russian separatists and said the shelling of one of its checkpoints on the border with Ukraine cast doubt on Kiev's peace plans. A Russian customs officer was wounded in the shelling, according to Moscow's foreign ministry, Reuters reported. The Kremlin said in a statement it would carefully review a proposal by President Petro Poroshenko for peace in eastern Ukraine, where a separatist rebellion erupted in early April. But it dismissed his declaration of a week-long ceasefire, saying it did not appear to include an offer of dialogue. "This is not an invitation to peace and negotiations but an ultimatum to militias in the southeast of Ukraine to lay down their arms," the Kremlin said. "So far one major element is missing - a proposal to start negotiations." It also said a Russian checkpoint on the border with Ukraine had come under "accidental or deliberate" mortar fire and demanded "an explanation and an apology" from Kiev. -- SPA 22:50 LOCAL TIME 19:50 GMT www.spa.gov.sa/1246046