The incident underscored the deep divisions between the various sides involved in trying to get Iran-backed rebels and the exiled government to agree to a badly-needed humanitarian truce.
Hamza al-Huthi, the head of the rebel delegation and from the Ansarullah group, was addressing reporters when a woman in a headscarf barged in and threw a slipper at him - a huge insult in the Arab world.
Al-Huthi promptly threw it back.
The melee lasted several minutes with bottles hurled before the intruders were hauled out.
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The woman's gesture was immediately hailed on social media in Aden, the main port city in South Yemen, with congratulatory tweets.
Once order was restored, al-Huthi said the rebels wanted "a humanitarian truce but it is not wanted by Saudi Arabia and its allies" who have staged aerial bombings on the rebels since March 26.
He said the stalled UN talks in Geneva would continue until at least tomorrow, adding: "We hope these preliminary talks will end up in some kind of accord ... A transition that will hopefully lead to free, fair and transparent elections."
Yaser al-Awadi, another member of the rebel delegation said the "Yemen war has become an economic investment for Britain, France and the United States."
"Their arms factories are working full-time for two months to furnish and supply arms," he said.
"Our women and children are being used as guinea pigs to test new arms," al-Awadi said at the chaotic press conference, the most dramatic event at the peace talks so far.
The negotiations, in their fourth day, have been bogged down by the government's insistence that the Iran-backed rebels must withdraw from the vast territory they control, including the capital Sanaa.