SANAA, Jan 17 (Reuters) - Shi'ite Muslim rebels killed two Yemeni soldiers in an ambush on Thursday, a senior official said, after sporadic skirmishes which threaten a six-month long truce.

"Supporters of (Abdul Malik) al-Houthi shot dead two members of the armed forces early this morning," the government official told Reuters, adding that 17 soldiers had been wounded in the attack.

Rebels loyal to Houthi accepted a truce in June, halting clashes that had killed hundreds and displaced thousands last year in Saada, a northern province of the poor Arab state.

"Dozens have been killed or injured on both sides in recent sporadic fighting in Saada," the official said, declining to give more details.

Rebel leaders could not be reached for comment.

The ceasefire required the rebels to give up their heavy weapons, and their leaders to go into temporary exile in Qatar, which helped mediate the deal. The truce also commits the Yemeni government to rebuild Saada, which the rebels say is neglected by authorities.

The conflict in Saada has been raging on and off since 2004.

In 2006, Yemen freed over 600 rebels in an amnesty but the latest bout of heavy fighting broke out in early 2007 when Houthi's backers attacked government checkpoints they complained had been installed deep inside the province as a provocation.

Sunni Muslims make up the majority of Yemen's 19 million population, while most of the rest, including Houthi and his supporters, are from the Zaydi branch of Shi'ite Islam.

Houthi's supporters oppose Yemen's alliance with the United States. Yemeni officials say they want to return to a form of clerical rule prevalent in the country until the 1960s. Western diplomats say the rebels may also want more autonomy. (Reporting by Mohamed Sudam; writing by Firouz Sedarat; editing by Sami Aboudi)

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