MOSCOW—Azerbaijan captured six Armenian servicemen in the early hours of Thursday morning, the defense ministries of both countries said, the latest twist in a simmering border dispute. The Azeri defense ministry accused the Armenian soldiers of trying to cross into Azeri territory. Armenia’s defense ministry said its soldiers had been carrying out engineering work in the border area of its eastern Gegharkunik region, which neighbors Azerbaijan. “Necessary measures are being taken to return the captured servicemen,” Armenia’s defense ministry said. Armenia earlier this month accused Azerbaijan of sending troops across the border, highlighting the fragility of a Russian-brokered ceasefire that halted six weeks of fighting between ethnic Armenian forces and the Azeri army last year. That conflict saw Baku drive ethnic Armenian forces out of swathes of territory they had controlled since the 1990s in and around the Nagorno-Karabakh region. Azerbaijan on Tuesday denied accusations by Armenia that it had …