By Pavel Polityuk KYIV (Reuters) -Russia has opened a criminal investigation after gunmen shot dead 11 people at a military training ground near the Ukrainian border, authorities said on Sunday, as fighting raged in eastern and southern Ukraine. Russia’s RIA news agency, citing the defence ministry, said two gunmen had opened fire during a firearms training exercise on Saturday, targeting a group who had volunteered to fight in Ukraine. The “terrorists” themselves were shot dead, it said. The incident is the latest blow to President Vladimir Putin’s “special military operation” in Ukraine and …