According to Otero, 7,900 people arrived in Andalusia in the first seven months of the year, nearly triple the number of arrivals in the same period in 2016.
Footage taken by a beachgoer shows a small boat full of people landing at a popular tourist beach in Spain's southern Cadiz province.
The main countries [from where the migrants arriving to Spain come] are Morocco, because obviously it's closer, but also they come from Sub-Saharan countries like Cote d'Ivoire, Guinea or Algeria, Gambia, but there are also people coming from Syria.
Migrants don't usually disembark on Spanish beaches but it has happened before, especially near the cities Melilla and Ceuta, which border Morocco.
"It's possible that Spain will outperform Greece this year", Millman told AFP.
At least 6,000 migrants have taken the latter route this year, with many looking to avoid lawless Libya and cross a shorter stretch of sea traditionally used to smuggle drugs, according to the European Union's border agency Frontex.
Some 11,849 people have arrived in Spain so far this year, compared to 13,246 in all of last year, the IOM says.
"If so, that's a big change".
Merkel famously opened Germany's doors to asylum-seekers in 2015.
Faced with the danger, some may be deciding to go up along the coast instead.
Spain's Guardia Civil police force said that nine of around 30 migrants who arrived on the beach on Wednesday had been found, all of them minors in their teens.
The number of arrivals from north Africa is likely to increase further due to the good summer weather, said Inigo Villa, head of the disaster management unit at the Red Cross.
"It's always surprising to see pregnant women and children - even if there aren't many - who try to cross in these conditions, risking their life and that of the kids for a better life".