A Syrian officer told pressmen that Islamic State militants retreating from Palmyra,laid thousands of mines that they planned to set off simultaneously as the army moved in.The officer said main streets and side roads in Palmyra had been rigged with explosives weighing up to 50 kg.More than 3,000 had already been safely detonated since government forces,backed by Russian jets,retook the city on sunday.He did not say why the Islamic State fighters failed to set off the explosives before pulling out,but his assertion echoed comments from Syria's antiquities chief,who said the militants intended to dynamite a greater area of the city's 2,000 year old ruins than they already had.The officer,who did not give his name,said the bombs left behind were linked so they could go off together.Islamic State's defeat in Palmyra was not only a significant military victory for President Bashar al-Assad,opening up the count...