BAGHDAD  Two sophisticated suicide bombings, including one on Tuesday in which 33 people died just outside Baghdad, and other recent violence are raising fears that jihadi militants and hard-line Baathists may be renewing their deadly partnership to threaten the largely calm Iraqi capital.

Iraqi military leaders emphasized that it was too early to draw any firm conclusions but noted similarities in the attacks in which more than 60 people were killed since Sunday. While overall violence in Iraq remains the lowest since the American invasion, both recent attacks were against Iraqi soldiers operating with relatively high security, suggesting much planning and coordination.

The worry among some Iraqi military officials is that Al Qaeda in Mesopotamia, a largely homegrown Islamist militant group, and Sunni insurgents loyal to Saddam Hussein and his Baath Party have put aside their differences to destabilize Iraq as the United States military proceeds with its plans to withdraw.

“We have said before that Qaeda was broken, but it was not finished,” said Hadi al-Ameri, the chairman of the Security Committee in the Iraqi Parliament and the leader of the Badr Organization, the former armed wing of the Islamic Supreme Council of Iraq, a Shiite political party.