SJENINA, Bosnia-Herzegovina (AP) _ Muslim refugees confronted a Serb roadblock and crossed a minefield Monday in a resolute effort to reach homes they had not seen in years. At least two Muslims were killed and a dozen injured.

A third Muslim died after being wounded in a separate clash with Serbs near Sarajevo, the Bosnian capital. A dozen other refugees were injured in that confrontation.

The Muslim-Serb disputes present a major challenge to the international peace effort, which is based on refugees' freedom to move about. Until Monday, no one had been killed in showdowns between would-be returnees and their former enemies, who don't want them coming back.

The U.S.-brokered agreement that ended the war provided no clear way to enforce its guarantee of freedom of movement. This forced the NATO-led peace force to enter the breach and start performing a task it had steadfastly resisted: scrambling to put out one dispute after another, well aware that any one could touch off new flareups in Bosnia.

Swedish and U.S. troops stood between about 300 Muslims and 25 Serbs at a checkpoint Monday near Doboj, about 60 miles north of Sarajevo.

When some Muslims tried to circumvent the obstruction by crossing a nearby minefield to reach their former homes, several blasts were heard and a dozen people were hurt, officials said. They later reported that two Muslims had died.

NATO spokesman Maj. Jerry Rehn said one was killed by small-arms fire of undetermined origin and the second presumably by a mine blast.

Maj. Paci Karonen, a spokesman for peacekeepers in Doboj, a few miles southwest of Sjenina, said seven dead or wounded had been evacuated by helicopter but that U.S. Apache choppers had spotted another five people still in the minefield. It was not clear whether any of those were dead.

There were conflicting descriptions of the incident.

A statement from the NATO-led peace force blamed local authorities for failed crowd control. It said small numbers of people had been allowed to cross at the same point Sunday, but the crowd Monday grew impatient and Muslim civilians began throwing rocks.

Muslim villagers gave a different story, saying the Serbs refused to let 20 people look at their houses on the other side, and that about 150 people crossed the minefield.

They said Serbs attacked them with small arms and grenades as they approached the nearby village of Kapetanovici.

Ema Jazavcevic, 48, was with her son Hasan trying to visit her house. When the attack began, she thought it was only warning shots from the peace force.

``When people around me started to fall, I crouched and closed my eyes,'' she said.

Bosnian federation police said six people were hurt, only one by a mine and five by small arms and grenades.

Near Sarajevo, Serbs blocked a convoy of Muslims from returning for a look at their homes and cemeteries in Trnovo, 18 miles south of Sarajevo. Fifteen people were hurt as Serbs battered their buses with rocks and sticks, breaking dozens of windows.

Bosnian TV said one of those hurt in that clash, Hajrija Kazazic, died in a Sarajevo hospital Monday night.

The convoy of seven buses, carrying up to 250 people, was attacked by about 100 Serbs soon after crossing into Serb-held territory near Sarajevo _ in spite of its escort, French troops backed by tanks and helicopters.

Another group of 200 Serbs stopped the convoy just north of its destination.

Zineta Belko, a 44-year-old Muslim refugee from a village near Trnovo, had boarded a bus Monday in hopes of seeing her home. She ended up in the hospital after a rock hit her in the head.

``I was very close to seeing my house, but I never got to see it,'' she said. ``I won't try to see it again. Normal life just doesn't appear possible with the Serbs.''

The French approach _ to try to force through the convoy to Trnovo _ contrasted with the attempts by U.S. and other peace force soldiers to discourage people from crossing the front lines.

Peace troops and officials said such moves, while inhibiting freedom of movement, were necessary to prevent violence from undoing months of painstaking progress in disengaging military forces.

A French spokesman, Maj. Herve Gourmelon, said the heavy military presence was meant mainly as a deterrent, but added that responding to such attacks is a police, not a military, job.