Kuwait has opened an international donors' conference for Syria with a pledge of $500 million in humanitarian aid for the war-ravaged country.

Emir Sheikh Sabah Al Ahmad Al Sabah made the pledge at the start of the gathering Tuesday in Kuwait. In his opening remarks, he said the Syrian conflict is the "biggest humanitarian crisis in recent history."

The civil war, now in its fifth year, has killed at least 220,000 people and displaced 11 million, according to U.N. figures.

Countries and organizations at last year's donors' conference in Kuwait pledged some $2.4 billion.

Ahead of this year's gathering, the German government said it will pledge $277 million in new aid.

Kuwaiti state media say local charities and aid organizations pledged another $506 million just before the conference started.