NVARD HOVHANNISYAN and NAILIA BAGIROVA AT least 16 military and several civilians have been killed in the heaviest clashes between Armenia and Azerbaijan since 2016, reigniting concern about stability in the South Caucasus, a corridor for pipelines carrying oil and gas to world markets. The clashes between the two former Soviet republics, which fought a war in the 1990s, were the latest flare-up of a long-running conflict over Nagorno-Karabakh, a breakaway region that is inside Azerbaijan but is run by ethnic Armenians. Nagorno-Karabakh said 16 of its serviceman had been killed and more than 100 wounded after Azerbaijan launched an…