Cairo - A bomb exploded at a Shi'ite Houthi mosque in the Yemeni capital Sana'a on Friday, wounding 13 people, a security source said, and the Islamic State claimed responsibility for the attack in a statement on Twitter.The bombing came against a backdrop of civil war in the country. Iranian-backed Houthi rebels have seized large swathes of territory, including Sana'a, prompting formation of a Saudi-backed Arab coalition that is using air power to try to halt their advances. Sunni Islamist militants have been seeking to extend their influence amid the chaos."Members of the caliphate in Sana'a have detonated an explosive device in a Houthi mosque in the people's district...which lead to the death and injury of many of them " said the Islamic State.According to a security source in Sana'a two out of the 13 wounded were in critical condition. The source added that the bomb was planted inside the mosque before Friday prayers.Earlier this year, a group of Islamist fighters in Yemen renounced their loyalty to al-Qaeda's leader and pledged allegiance to the head of the ISIS.In April, a new branch of ISIS in Yemen issued a video showing what it said was the beheading of four Yemeni soldiers and the shooting of 10 others.Al-Qaeda in the Arabian Peninsula (AQAP), al Qaeda's Yemeni wing, has killed hundreds in attacks across the country in recent years and has taken advantage of fighting in recent months to consolidate its hold in eastern regions.