Ameera Dawoud is a Christian, but as soon as the Islamic holy month of Ramadan began, she traded her pants, fitted skirts and uncovered hair for oversize clothes and a veil.

"They say you have to cover your hair or we will kill you," Dawoud said by telephone from the northern city of Mosul. "If you don't wear a veil, people look at you as if you were naked."

Some Christians in Mosul feel say they are being subjected to threats that have escalated during Ramadan (search) and that may be designed to drive them out of the country, create religious tensions, or at least make life difficult.

Even those who haven't received threats swap stories of anonymous phone calls and pamphlets plastered on walls or slipped under doors warning those who don't dress like devout Muslim women during Ramadan.

Coupled with a series of attacks on churches in Mosul and Baghdad — and a general fear of insecurity gripping Muslims and Christians alike — some Christians have chosen to leave Iraq at least temporarily. Those who stay try to maintain a low-profile or play it safe and just follow orders.

"Things weren't like that. During last Ramadan, we used to wear what we wanted and to go out whenever we wanted," the 30-year-old Dawoud said. "Now, I'm terrified, very scared."

She said one of her friends left for Turkey after receiving death threats unless she converted to Islam.

Pascale Isho Warda, a Christian who is the interim government's minister for displacement and migration, has estimated as many as 15,000 out of Iraq's nearly 1 million Christians have left the country since the August attacks on churches.

A Catholic bishop in Mosul, Georges al-Qas Moussa (search), said the threats against Christian women who don't wear veils during Ramadan seem to be the most common type of threat. But some Christians were told that their homes would be seized or they must convert.

"Officially there is no problem, but the pressure is coming from unknown parties," Moussa said.

Mosul's Christian minority has for long lived in harmony with the city's Sunni Arab majority, and many say they still do. Any hostility toward Christians was mostly kept in check under Saddam Hussein, who didn't allow militant Islamists to gain clout.

The rise in Islamic fundamentalism after Saddam's ouster worries Christians, secularists and some moderate Muslims.

After the U.S.-led invasion, there was a period when Mosul was a quiet city, touted as a model of success for the American military. Then attacks against U.S. forces increased, followed by a spike of attacks on police and those civilians seen as collaborators. Assassinations and kidnappings have become common, haunting locals and scaring away many foreign journalists.

On Wednesday, Iraqi authorities imposed a curfew on Mosul after clashes erupted there, the U.S. military said.

In August, four churches in Baghdad and one in Mosul were blown up in a coordinated series of car bombings. More churches have been attacked in Baghdad since then.

Salem al-Haj Eissa, a provincial council member and a member of Mosul's local administration, said that in general much of the trouble in Mosul comes from fighters who moved to the city to escape military operations elsewhere in Iraq or who illegally crossed over from Syria.

Some of Iraq's most feared terror networks, such as the Ansar al-Sunnah Army (search) and Al Qaeda in Iraq (search), have claimed responsibility for attacks in Mosul.

But Eissa doesn't think that any of the big groups are behind the intimidation of Christians. He blames the threats on marginal figures who have no knowledge of true Islam.

"Everyone has a computer and anyone with a sick mentality can print out a leaflet," he said. "These groups want to create chaos and tensions toward Christians."

Bishop Moussa said some criminal groups mask their intentions in religious garb and make threats just to blackmail Christians. Others do it out of ideological stances or political beliefs.

"They want to undermine security and pressure the government," he said. "But there are also extremist, fundamentalist currents ... that are against the religious presence of the other."

He added that some mistakenly equate Iraqi Christians with Christian America.

"The people want to live in peace and security. When they receive threats and get harassed they leave," he said.

Dawoud said her parents stopped going to church for fear of attacks.

"Most of my friends have left," she said. "We had a priest whose room was broken into and he left as well."

She wants to stay in Iraq. But she wants things to change.

"When you cannot dress the way you like or go out when you like, you feel your freedom is being robbed," she said. "If your freedom is taken away, then you're worth nothing."