In eastern Ukraine there has been a series of explosions at an arms factory under the control of pro-Russian separatists in Donetsk.
The blasts caused munitions to detonate.
The former Soviet weapons factory is about ten kilometres from the city’s airport, which is controlled by the Ukrainian army.
Rebel sources are quoted as saying a shell hit the factory. But other reports say residents have said on social media that bombing was not the cause.
Hours earlier negotiators at peace talks in Belarus signed a memorandum to create a 30-kilometre buffer zone between government troops and separatists, who Kyiv says have been reinforced by Russian arms and soldiers.
Weaponry is being moved back in an attempt to help implement the ceasefire accord agreed earlier this month which has repeatedly been broken by clashes.
Russian media say a third convoy carrying humanitarian aid from Russia has arrived in Donetsk, following two others which were sent over the past month without being authorised or checked by Ukrainian authorities.
The Russian reports say Ukrainian authorities and the Red Cross turned down repeated invitations from Moscow to inspect the contents.
Kyiv has said Ukrainian guards would not be able to check the latest convoy as they do not control the border crossing.