LONDON — Haggard and defiant, a large number of migrants marched from the Keleti train station in Budapest toward Germany on Friday, pledging to walk 300 miles rather than remain in a country where they are not welcome.

“This is going to go down in history,” said Rami Hassoun, an Egyptian migrant from Alexandria who was helping corral the crowds on a six-lane highway, where the migrants were being watched by the police.

The police put the number of migrants who were walking at 500, but photographs from the scene and eyewitness accounts suggested the figure was at least twice that.

Other migrants remained locked in a tense standoff with the police at the Bicske station outside Budapest, while more stormed out of a camp in the country’s south, highlighting the desperation of migrants determined to flee Hungary.