NAIROBI/ADDIS ABABA (Reuters) -A fresh eruption of fighting in northern Ethiopia has raised concerns among residents about the safety of rock-hewn churches in the town of Lalibela dating back to the 12th and 13th centuries. Fano militiamen fighting the Ethiopian army in the Amhara region over-ran Lalibela and Gondar for several days in August marking Ethiopia's most serious security crisis since a two-year civil war in the neighbouring region of Tigray ended a year ago. In a separate incident hi