Most of the group of about 400 travelers who arrived in border city Tijuana on buses over the past couple of days said they intended to legally seek asylum in San Diego later on Sunday, but lawyers advising the group gave them stark advice - not everyone will be successful.

After the grueling journey, a somber mood took hold as the reality sank in that many of them would be separated from their families. Lovers and parents with slightly older sons and daughters could be forced to split up.

At venues around the city, U.S. immigration lawyers working on a pro bono basis on Saturday listened to harrowing tales of life in the immigrants' home countries.

Death threats from local gangs, the murder of family members, retaliatory rape, and political persecution back home prompted them to flee, the migrants and lawyers say.

Many of the immigrants who spoke at length with Reuters at various points during their trip through Mexico had been short on knowledge of their legal rights, but at least 24 recounted detailed stories of facing death threats.

As poor migrants from Central America on a perilous route through Mexico, they feared they could be robbed, raped, arrested and assaulted, so traveling by caravan offered their only protection, they said.

The lawyers advised which cases had higher chances of passing the "credible fear" test required to enter the long and often difficult U.S. asylum process, said immigrant rights organization Al Otro Lado, Spanish for On the Other Side.