ATHENS—Greece's parliament passed a package of austerity measures on Thursday, a key condition of its €110 billion ($145 billion) financial rescue, as thousands of protesters demonstrated outside the chamber, some hurling firebombs and clashing with police. The vote came the day after three people were killed in violent protests against the measures, saddening a nation already struggling with economic hardship. The White House said President Barack Obama was briefed on the situation in Europe and on the markets Thursday afternoon by Treasury Secretary Timothy Geithner and economic adviser Larry Summers. While Europe's financial struggles played a role in driving down...