Al Jazeera's Hashem Ahelbarra reports on the government troops reported to have clashed with Shia fighters in northern Yemen, hours after a mosque was bombed.

Funerals are being held for the 18 worshippers killed, who included soldiers from a nearby barracks.

The attack in Sa'ada adds to the thousands already killed in a four year conflict. It also throws into a doubt a peace deal revived earlier this year.

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