MOSCOW, Aug 10 (Reuters) - Five Ukrainian soldiers, who were detained after crossing the border into Russia, have been released back to their unit, which is fighting separatists in eastern Ukraine, Interfax news agency quoted a Russian law-enforcement source on Sunday as saying.
The five were among some 300 Ukrainian soldiers and border guards that Ukraine said were forced by fighting to cross into Russia on Monday.
Most were returned to Ukraine but Russian investigators said on Friday the five were detained on suspicion of shelling civilian areas of eastern Ukraine and firing into Russia - a frequent Russian complaint against the Ukrainian military.
"The transfer of the battalion commander of the 72 brigade and four subordinate officers took place overnight to Sunday," the security services source told Interfax.
The handover took place at the Chertkovo checkpoint, on the border between eastern Ukraine and Russia's Rostov province, the source said.
A Ukrainian military spokesman said in Kiev on Thursday the five were among 18 against whom Russia had opened criminal investigations. Twenty-eight Ukrainian border guard officers were also being held in Russia, he said.
Kiev is fighting a rebellion which began in April in its Russian-speaking eastern provinces, where Ukraine and its Western allies believe Russia has actively supported and armed the rebels. Moscow denies involvement.
The United States and the European Union have imposed sanctions on Russia over its role in the fighting and over Moscow's annexation of Ukraine's Crimean peninsula in March.
Moscow has retaliated with counter sanctions, imposing sweeping trade restrictions of Western food imports. (Reporting by Alissa de Carbonnel; Editing by Alison Williams)