NVARD HOVHANNISYAN, NAILIA BAGIROVA and STEPHANIE NEBEHAY AZERBAIJAN and ethnic Armenians have fought with artillery and heavy guns as the United States, France and Russia stepped up efforts to secure a ceasefire and avert a wider war in the South Caucasus. Azerbaijan said the city of Ganja had come under fire, deep inside its territory. Ethnic Armenians who control the mountain enclave of Nagorno-Karabakh inside Azerbaijan said Stepanakert, its main city, had been shelled by Azeri forces. In a sign of growing alarm in the region, the head of a six-country military alliance led by Russia and including Armenia warned…