Henry Onyekuru has scored 11 goals for Eupen this season
Onyekuru, 19, was heavily linked with a move to Celtic in the latter days of the January transfer window.
The left-sided playmaker's agent also revealed last month that Liverpool want to sign him.
But reports in Spain claim Sevilla are ramping up their interest and hope to get a deal in place by the time the summer transfer window opens.
That is according to Spanish newspaper Estadio Deportivo, who claim Sevilla's sporting director and recruitment mogul Monchi is tracking Onyekuru closely.
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He asked me specifically about Celtic
Onyekuru has scored 11 goals in 24 appearances this season, helping KAS keep float in the Belgian Jupiler League's relegation scrap.
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Fenerbahce are also said to be eyeing Onyekuru, with a source last month telling website Owngoalnigeria that his agent is keen to secure him a deal to a top European club.
”His agent told me about Liverpool’s interest yesterday when I tried to re-ignite Fenerbahce’s interest in his services," the source said.
"I don’t how long Eupen can hold on to him, he is a very good player.
”He (Onyekuru) will most likely leave Eupen before the end of this transfer window despite their hard stance.
"They could be forced to cash in on him."
Liverpool and Celtic were linked to Onyekuru (left) as recently as last month
Eupen sit third bottom of the Belgium top flight
Celtic's interest in Onyekuru is said to have sparked as manager Brendan Rodgers seeks the next big talent in European football, having already secured a bargain in Moussa Dembele from Fulham last season for just £500,000.
And fellow Nigerian Peter Odemwingie told the Daily Record last month that Onyekuru had been in touch.
"He asked me specifically about Celtic and I told him first and foremost they are a big club, they give youngsters a chance and it's a step closer to the English Premier League," Odemwingie said.
"Even for someone like me looking in from the outside I was able to list so many positives about moving to Celtic and he seemed to agree – but he had other options. Once we had our conversation it was out of my hands."
It is claimed Leipzig, Anderlecht and Nice are also all interest in signing Onyekuru.