A violent explosion that destroyed a holy Shiite shrine renewed tensions between Shiite and Sunni Muslims in Iraq Wednesday sparking fears that the country could descend into civil war.

GWEN IFILL: Welcome back, Ed. It seems like there have been weeks now of escalating attacks in Iraq, and today's was certainly spectacular. The question is: How significant was it?

EDWARD WONG: Hi, Gwen. The attack today was fairly symbolic, and it basically had consequences across the entire country. What you saw was -- you saw protesters streaming out into streets in cities all across Iraq, whether it was down in Basra in the South by the Gulf or up in Kirkuk in the North.

A lot of them were calling for some sort of retaliation. Some of the protests were peaceful, but there were also attacks on dozens of mosques in retaliation. Many of the attacks were on Sunni mosques and various political leaders had to come out and basically call for restraint, call for calm. We saw Grand Ayatollah Ali al-Sistani, the Shiite cleric, come out and say that he wanted a period of mourning but he did not want violent reprisals.

We also saw some other Shiite leaders coming out and saying the same thing. And the top American general here and ambassador also came out to try and conciliate between the different parties. So basically it was a huge deal among all the leaders here, all the politicians, the religious leaders, all of them had to come out and try and calm people down.

GWEN IFILL: You have made reference to the U.S. ambassador to Iraq, Zalmay Khalilzad, who on this program yesterday was talking repeatedly it seemed about the problems of sectarian political division, and now we see what appears to be sectarian violence. Is there generally considered to be a connection?

EDWARD WONG: The sectarian attacks have been going on for quite sometime now in Iraq. Basically for at least a year or more we've had a low level of civil war here, even though many people don't want to call it a civil war. But everyone on the ground here undoubtedly thinks there is one. So far, we're not - as far as we can tell - we're not heading towards a large-scale civil war anytime in the coming days.

But sectarianism - violence related to sectarianism has been here. There have been bombings that have killed 130 people at various mosques and those have been in some ways just as devastating as the attack today. So the fact that there is this sectarian-oriented attack isn't that new; it's just that they decided to attack one of the most significant shrines in the world of Shiite Islam.

GWEN IFILL: In fact, Samarra is one of the four holy cities in Iraq. So when the United States officials on the ground there watched this, did they fear that because of this symbolism it may undermine the political process they've been trying to jump-start?

EDWARD WONG: It's definitely created a lot of tension. And some of the Shiite leaders are even blaming that on the Americans, saying that the Americans haven't been conciliatory enough in this process, that the Americans have been upping the tension by using the wrong language, by underscoring the divisions, by calling for various quotas, for example, in the government.

So the Americans have been trying to act as a middle person in this process, and now you have these groups that are still far apart in their talks and that are also feeling alienated from the Americans and from each other. So this attack only serves to exacerbate that, and we're seeing groups, you know, calling for calm today but we're not seeing them really moving close together yet.

GWEN IFILL: We have over time, talking to you and others about the situation in Iraq, found out - had questions about the role of Muqtada al-Sadr, who has quite a following, and a connection, as well, to Iran. Have we heard any reaction at all from him or his followers?

EDWARD WONG: Well, Muqtada's officials, his high-ranking officials in his organization came out in a press conference and basically also called for restraint, just like many of the other Shiite leaders did, including Ayatollah Sistani, but in Sadr City what you saw was just some members of Muqtada al-Sadr's militia driving around with Kalashnikovs, driving around in cars, and there were - was a lot of anger there.

A lot of it was directed at Americans; it was directed at both Sunnis and at terrorists or insurgents, but a lot of them were also blaming the Americans for what had happened and oftentimes you do hear this rhetoric, you do hear this talk at a lot of bomb sites.

And Muqtada's people have been especially anti-American and he's never backed down from that stand. So you do have a lot of angry young men out there with guns who are angry at not only Sunni Arabs but also at Americans and at other occupying powers here.

GWEN IFILL: So does that mean anytime something like this happens even if it is clear -- fairly clear that it is Iraqis essentially attacking Iraqis that Americans by their very presence there will also come under question or suspicion?

EDWARD WONG: The problem that the Americans face here in Iraq is that basically people on all sides believe that the hand of America is in everything. So, I mean, I think that they see America as a superpower and they know its presence in the world and they know its presence here in the country and so when there's an attack, when there's political happenings, whatever you call it, they'll believe that there is some element of American involvement in it.

The other power that many people are starting to look towards is Iran and you'll see a lot of talk of people seeing that, you know, Iranian involvement in attacks or in various sectarian killings and that's something that various political leaders are trying to grapple with right now.

GWEN IFILL: President Talabani called this attack today "a conspiracy against the Iraqi people to spark a war among brothers." What was he getting at there?

EDWARD WONG: Well, for a long time now we've heard talk that there were certain guerrilla cells or terrorist cells who want to start a civil war, basically sparking a sectarian war between Sunnis and Shiites. I mean, the letter that Abu Musab al-Zarqawi, the Jordanian militant, sent to certain leaders basically said that he wanted to spark a sectarian war. And we know that that's part of the strategy of certain militant Sunni Arabs, as well as other types of insurgents, maybe Iranian-backed insurgents - we're unsure about that -- but there is the strategy to do that and basically Talabani and other leaders are trying to pull people back from that. They're trying to pull people away from that precipice.

GWEN IFILL: Ed Wong, thank you as always.

EDWARD WONG: Great, thanks a lot, Gwen.