The pacifist party, which is the junior partner in Chancellor Gerhard Schröder's government, has been deeply split over Germany's participation in Nato air strikes.

Foreign Minister and Green leader Joschka Fischer was hit by red paint

Delegates on their way to the conference had to battle their way past ranks of anti-war protesters, many carrying posters of Chancellor Schröder and Green Party leader, Joschka Fischer, daubed with Hitler moustaches.

Inside the hall, the party's grass-root supporters displayed their anger and some Green cabinet ministers were hit on the face by eggs thrown from the audience. Mr Fischer was hit on the shoulder by a bag of red paint.

Scuffles followed as demonstrators tried to hang peace posters behind the podium before being led away.

Fundamental principles

The BBC's Terry Stiastny: "Protests against the German Green Party's support of Kosovan war"

Greens on the far-left of the party have argued that German participation in the Nato campaign is wrong and should be stopped immediately. They say the fundamental principles of the Green Party are at stake.

But self-styled "realist" Green MPs argue that the bombing is both necessary and justifiable.

Mr Fischer, who also holds the post of foreign minister in Chancellor Schröder's cabinet, has warned his party not to back calls for an indefinite Nato ceasefire. He has reportedly said he will resign if the proposal, which is against government policy, is passed.

Threat to unity

"Fischer: You're done!"

If such a measure was approved it would make the Green's continuation in government impossible, and would mean an end to the red-green coalition just eight months after it took power.

It would also be a damaging blow to Nato unity.

The party leadership has proposed an alternative resolution, calling for a temporary ceasefire to allow new negotiations on Kosovo.

The BBC's Bonn Correspondent, Caroline Wyatt, says the party now faces a key decision on whether to stick to its pacifist principles and return to the political sidelines, or to stay in government and try to influence policy from within.