SANAA (Reuters) - At least two people were killed on Saturday when supporters of Yemen’s ex-president Ali Abdullah Saleh clashed with Houthi fighters in Sanaa, marking unprecedented violence within the alliance fighting a Saudi-led coalition.

Members of the presidential guard exchanged gunfire with the Houthi fighters who had tried to set up a security checkpoint near the home of Saleh’s son and his media office in an upscale district, residents said.

Intermittent fighting continued for several hours, cutting off access to a main road in the Hadda neighborhood, they said.

The Houthi-controlled state news agency SABA said two members of popular committees were killed in the violence. Media reports of more casualties on both sides could not immediately be confirmed.

The tactical alliance between Saleh and the Houthis has often appeared fragile, with both groups suspicious of each other’s ultimate motives and sharing little ideological ground.

Saleh rallied thousands of supporters in Sanaa on Thursday in a show of force a day after Houthi fighters decried him as “evil” and condemned his description of them as a “militia”.

Both sides jointly run northern Yemen and have been fighting the internationally recognized government, based in the south and backed by the Saudi-led coalition, for 2-1/2 years.

The coalition intervened in the civil war in 2015 to restore the government to power in Sanaa. But the conflict, which has killed at least 10,000 people, is in stalemate.

Big switches of loyalty are a feature of Yemen’s byzantine political landscape, particularly since 2011 “Arab Spring” unrest which led to Saleh’s fall in 2012.