[A Greek national flag flutters atop the parliament building in Athens]ATHENS (Reuters) - Greece's parliament on Sunday passed a package of unpopular pension and tax reforms that the country's leftist-led government hopes will help persuade official creditors to release bailout cash. After a two-day heated debate and amid protests and strikes by labour unions, Prime Minister Alexis Tsipras' coalition, which has a thin parliamentary majority, secured enough votes to pass the reforms ahead of Monday's Eurogroup meeting. (Reporting by George Georgiopoulos and Renee Maltezou)