Martínez has reportedly been a long-time transfer target for the Gunners and is expected to head to Italy for a medical next week after Milan agreed to pay his €35 million release clause.
In his three seasons in Portugal, Martinez has scored 67 league goals, seeing him emerge as one of Europe’s most sought-after forwards.
The hitman won the Portuguese league with Porto during the 2012/13 season, and was on target in a shock first-leg win over Bayern Munich in the quarter finals of this season’s Champions League.
“Jackson Martinez has chosen Milan,” Porto president Pinto da Costa told Porto Canal.
“Before going on holiday Jackson announced he wanted to leave. The €35m clause is not up for debate and must be paid. I learned just now that Jackson has chosen Milan. This is what he wants, the destination is irrelevant as far as I am concerned. I want him to be happy.”
Martinez is currently on international duty with Colombia at the 2015 Copa America, where he will be hoping to help his country to a first tournament win since 2001. His reported new club AC Milan finished last season in tenth place in Serie A.