Three young Christian women in a predominantly Christian Nigerian town recently took a taxi to a wedding. They wore bright pant suits, lipstick, and rouge. "Can you imagine sharia coming here?" I asked.

"If it did, we couldn't step out of the house in pants," said one. "And you wouldn't be able to ride with us in this taxi because you're a man."

Another said, "You wouldn't be able to comment on how pretty we look either. If you did, the police would probably arrest you."

The Christian women and the Muslim taxi driver laughed together.

This was the lighter side of the interaction between Christians and Muslims in Nigeria. The darker side is that conflicts over sharia--strict Islamic law--have sparked riots, caused deaths, and threatened to destroy the democratic government Nigerians elected last year.

Sharia is the Islamic penal code. In countries like Iran and Afghanistan, Islamic clerics apply it under a theocracy. Under sharia, adulterers can be stoned to death and thieves can have their hands cut off. Less extreme measures are taken to stem a multitude of social ills.

In Africa, implementing sharia is rare. Most prefer Islam in the home, the street, and the mosque, not in parliament. They want to mix Western civil liberties with personal faith. Some elected officials in Nigeria, however, are trying to institute and enforce sharia now.

To understand the terror that's gripped several towns in this Texas-size country of 110 million, one has to understand Christian and Muslim interactions in Nigeria--a relationship whose difficulties are compounded by ethnic and tribal tensions, apart from religion.

Being from the "other" religion is the first risk a person runs from day to day. Then comes ethnicity. There are three dominant language groups--Hausa, Yoruba, and Ibo. Four hundred smaller groups, mostly unrelated to the big three, break people further apart. Each has their own creation myth and rites of passage. Members of different groups have different scars and dyes on their faces. They are four hundred ancient nations seething within one modern one.

In October, the governor of the northern Nigerian state of Zamfara--one that is 90% Muslim--established sharia as a remedy for unemployment and immorality. "What I am trying to do is ensure that my society is very pure," he said. "It is mostly drug-abusing people who are, you know, alcoholic and so on that will take arms and go and kill somebody." Gambling and alcohol sales were banned in the region. Boys and girls were put in separate schools. Muslim women in search of a ride have to wait until they see yellow taxis with the symbol of a veiled woman painted on the doors. The fear is that men or women will get aroused when they are close to each other, and sex could easily follow. The governor and his supporters claim that fear of punishment will prevent people from breaking the law.

February was a bloody month. More than a thousand people were killed in clashes over sharia in different towns. People here kill either to prevent or to allow the law to come to their town. Nigerian President Olusegun Obasanjo has asked the pro-sharia politicians to stop, but they say they will continue and go to court if necessary.

The Zamfara governor has repeated his stance to the press. In late March, he approved the cutting off of a local man's hand. One morning, the man stood in a sharia court accused of stealing a cow. By the afternoon, his right hand was removed. The man is a Muslim, but tells newspapers in Nigeria that he will appeal his case.

Other religious tensions are apparent in a scene from one of Nigeria's overnight buses, which passengers board in the evening and ride until the morning. In Nigeria, bandits ambush vehicles in order to rob and kill, so a Christian bus rider makes an impromptu call for protection to ward off such an attack.

"Can I hear hallelujah?" says the man, standing in the aisle, shouting into the microphone attached to the bus's public address system.

"Hallelujah," say about half the passengers.

"May God bless this bus and cover its riders with the blood of Jesus. As we travel on this road, are you prepared to put your life in the hands of Jesus?" Christian passengers begin singing, clapping, and praying.

The next morning, when the bus driver refuses to let a passenger get off where he wants, a Muslim passenger yells, "Preaching in public places is illegal. You Christians are fanatics. May God bring sharia down on you, your children, and grandchildren." None of the other Muslims react. This Muslim, a university graduate, spent many years abroad. He later said that he doesn't support sharia; frustration had simply overtaken him. It was also not clear whether the bus driver was discriminating against him. But the habit of distrusting others who don't belong to your mosque, church, or tribe threatens peace.

Sharia proponents say the president has no constitutional power to stop its implementation. And while politicians are still fighting with words, ordinary people are fighting with weapons.

A 33-year-old truck driver who would only give his name as Chuks told me what he considered to be the proper response to violence against his people, the Ibo (Ibos are Christian). He had driven to the northern city of Kaduna, where a company needed a truck to transport the corpses of 100 dead Ibos to their ancestral homelands in the south-east.

The regular driver, a Muslim, refused the assignment. Chuks agreed to drive the bodies. He relished describing what happened once he reached the safety of Umuahia, where the majority is Ibo and Christian like himself:

"When we got there, our people knew what to do. We shot guns and filled bottles with chemicals--they explode when we throw them," Chuks said. Then he and his friends attacked people whose crime was to worship in a different house and speak a different language. "We found the Hausas in our village and showed them what it means when you kill Ibos. We killed plenty of Hausas."

Though the widespread violence has forced other states to reconsider introducing sharia as law of the land, it's anyone's guess how long this relative calm can last. Judging by the words of people like Chuks, there is little reason for optimism.