Some 800 migrants headed from Istanbul in Turkey to Edirne, a city to the northwest, as they are trying to cross into Bulgaria and thus reach the EU, media sources say.

According to a Turkey correspondent for the Bulgarian National Radio, they were trying to reach Bulgaria or Greece's borders by bus and give either border a try.

Turkish authorities, however, did not allow them to get on the buses at the Esenler station in Istanbul - one packed with migrants which have been disrupting bus schedules there over the last few days.

An Esenler official is quoted as saying that some of the companies stopped issuing tickets migrant willing to travel west had already overcrowded most buses, while others decided to deny trips to people without documents.

Most migrants are seeking to reach Germany and some opt for another Western country. They use routes via Greece, Macedonia, Serbia and then Hungary (the first Schengen country on their way), though some still decide to pass through Bulgaria, entering from Turkey.

Arab Studies expert Prof Vladimir Chukov on Monday told private national NOVA TV station that some Arabic-language newspapers were already showing photos of "refugee candidates" willing to travel to Germany via Bulgaria.