They are said to be mostly from Morocco. Spanish media says Moroccan border guards did not stop them.
It's been over the years that spain's Ceuta and Melilla have become magnets for African migrants.
Early reports on Monday said more than 100 people had come overnight and we're mostly young men but also children and several families included.
They were taken to a migrant reception centre. But as more turned up later in the day, officials said the number had risen to 5,000 an unprecedented figure which they warned could rise further.
However, Spanish Foreign Minister Arancha González Laya said some migrants have already been sent back home.
Authorities says last month, more than 100 migrants arrived in spain and most of them were sent back, except about 30 minors whose ages were confirmed by medical tests.
The EU border force Frontex reports that illegal migration to Spain's Canary Islands off the Moroccan coast has surged this year. In most cases sub-Saharan Africans make journeys in rickety boats and drowning is common.
However, the overall numbers of undocumented migrants reaching Europe so far this year remain far below the levels seen in 2015-2016.
Content created and supplied by: Hon1 (via Opera News )
Opera News is a free to use platform and the views and opinions expressed herein are solely those of the author and do not represent, reflect or express the views of Opera News. Any/all written content and images displayed are provided by the blogger/author, appear herein as submitted by the blogger/author and are unedited by Opera News. Opera News does not consent to nor does it condone the posting of any content that violates the rights (including the copyrights) of any third party, nor content that may malign, inter alia, any religion, ethnic group, organization, gender, company, or individual. Opera News furthermore does not condone the use of our platform for the purposes encouraging/endorsing hate speech, violation of human rights and/or utterances of a defamatory nature. If the content contained herein violates any of your rights, including those of copyright, and/or violates any the above mentioned factors, you are requested to immediately notify us using via the following email address operanews-external(at)opera.com and/or report the article using the available reporting functionality built into our Platform See More