Seven Sunni construction workers were killed by unidentified gunmen who fired on them from a speeding S.U.V. on Tuesday morning in Abara, a majority-Sunni village in Diyala Province, police and medical officials said. When their families took the bodies to a ritual washing hall, a bomb exploded, killing six family members, two women and four men. That evening, a suicide bomber targeted a Shiite shrine in Diyala, killing 12 Shiites. “Al Qaeda has succeeded in its strategy,” said Haider al-Musawi, a security expert and former army officer. “Now Sunnis think that the Shiites are killing them, and the Shiites think that the Sunnis killed them.” He said the situation could become worse than Syria barring an immediate solution, which would be “a miracle.” The 25 were among 31 people killed in Iraq on Tuesday.