A suicide car bomber struck a convoy of Yemeni Shiites on their way to a religious ceremony yesterday, killing 17.
Al-Qaida is suspected to be behind the attack, although it would be the organisation's first reported direct assault on the country's Shiite minority.
Yemen's al-Qaida has been increasingly active over the past year, assaulting government targets inside the country as well carrying high profile attacks abroad such as last month's attempt to send parcel bombs to the US in cargo planes.
While the militants have always been rhetorically extremely hostile to Yemen's Shiite community, they have not attacked them directly in Yemen, unlike in Iraq where the sectarian warfare is more pronounced.
Like many Arab countries throughout the region, Yemen's Muslim population is split between the majority Sunnis sect and Shiites, whom hardliners often describe as heretics.
The Yemeni official said the attack took place in al-Jawf province, 109 miles north-east of the capital, Sanaa and those killed were supporters of the Shiite Hawthi rebels, a tribal group who have waged an on-and-off uprising against the government.
The attack comes two months after al-Qaida accused the Hawthis of grabbing two of its members and handing them over to the security chief of Saada province. Since January 2009, when al-Qaida's battered Saudi and Yemeni branches merged to form al-Qaida in the Arabian Peninsula, the terror group has become increasingly bold, directing attacks in the capital and across the countryside against officials and foreigners.
Apart from the al-Qaida threat, Yemen's weak central government has also struggled with a separatist movement in the south and the Hawthi rebels in the north.