Real Madrid have recently been linked with a move for Martinez, with reports claiming the Spanish club had made an enquiry about the striker.
Premier League quartet Arsenal, Chelsea, Manchester United and Tottenham Hotspur are also reported to be admirers of the Colombia international.
Barcelona, meanwhile, are reported to be weighing up an offer for Mangala, with the centre-half another Porto player to have been linked with a move to the Premier League in the past.
However, Pinto da Costa has dismissed reports that Porto have fielded any approaches for the influential duo.
"Every day there are stories that one club or another wants Mangala but Porto have not received a single offer for him," the Porto supremo told EFE.
"It is the same with Jackson. His name has been in every paper but nobody has contacted us about him."
Otamendi has attracted speculation linking him with the likes of AC Milan, Chelsea and Atletico Madrid, but again Pinto da Costa claims that none of the rumours are true.
He added: "Otamendi is the other name that people always talk about and no offers have been received for him either."