It is a situation that has reduced nearly every Iraqi to living in fear. The attacks do not appear to discriminate between the country's disparate national and religious groups.
For Iraq's minority groups, it is especially difficult. The country's Assyrian Christian community, for one, says it fears its churches will become the next target of a terrorist attack.
"Our branch here in Baghdad received a report warning us, 'You have to inform the chairman to take care. We have some information.' They didn't declare what kind of information, but we depend on the report that we received and we take the subject seriously."
More than one million Assyrians are believed to be living in Iraq. Most are in Baghdad and central Iraq, but large communities can also be found in the north and south of the country. Assyrians are the only group in Iraq that still speaks Aramaic, an ancient Semitic language spoken by Jesus and his disciples.
Assyrians lived relatively peacefully under Saddam Hussein -- one of his top aides, former Foreign Minister Tariq Aziz, is himself an Assyrian Christian.
Now, however, no group seems safe from attack. Warda says many Christian churches are responding to the anonymous threats by cutting back the number of services and working only during daylight hours.
"All the churches now are paying attention to these kinds of threats, and they are changing the time [of their services]. Even churches which used to hold meetings for youth and things like this are postponing them and neglecting some lectures for youth and for women."
Iraqi Muslim organizations say the threat is not coming from them.
Al-Hawza al-Ilmia is a powerful Shi'a movement based in the holy city of Al-Najaf and led by Grand Ayatollah Ali al-Sistani. Hawza's Baghdad representative, Sheikh Abd al-Jabbar Menhal, says his group condemns unconditionally the threats against the Christian churches.
"We heard about the signs that [Christian churches] might be attacked, and we condemn such operations, because Islam respects all sacred places, like mosques, churches, et cetera."
Neil Partrick is an analyst with the Economist Intelligence Unit in London. He says few Iraqi political or religious groups can feel safe in the current climate in Iraq.
There are a number of elements in the country who might wish to attack the Assyrian Christian minority, Partrick says -- including radical Sunni groups frustrated by their community's loss of prestige and power following the fall of Hussein.
"It's very hard to generalize, but if one looks at the national picture, then certainly the targeting of very obvious sectarian or religious identities -- [as opposed to] political religious ones -- is mostly likely to come from Sunnis, who feel dispossessed from the changing political situation."
Partrick says Al-Qaeda or remnants of Hussein's regime could also be to blame for the threats, and that the source may vary from region to region.
(Sami Alkhoja contributed to this story from Baghdad.)