The main Belarusian opposition leader has begun serving a jail term for leading a rally police said was illegal. Alexander Milinkevich has been sentenced to 15 days and has described himself as a political prisoner. He told journalists that the police had said the march was unlawful but only afterwards. “They did not say through loudspeakers that we could not hold the rally. I told them it was a legal gathering,” he said.Other leading figures who oppose veteran leader Alexander Lukashenko were also rounded up after Wednesday’s rally. Milinkevich stood and lost against Lukashenko in a presidential vote last month that Western observers say was rigged. Lukashenko is is popular in large swathes of the country. Thousands of people took part in the demonstration, which marked the 20th anniversary of the Chernobyl disaster, traditionally a focal point for anti-Lukashenko protests.