The Sunday Telegraph says City attempted to acquire both players at the end of the January transfer window but the deals could not be completed in time. However, City's director of football, Txiki Begiristain, is understood to have continued the negotiations.
The deal to sign Mangala, a rangy 23-year-old central defender who is a France international, is the most progressed, with sources in Portugal claiming yesterday that the fee could be as high as £29 million.
Fernando's agent has hinted that the holding midfielder could join City, after a move for him also stalled in January, and the player is expected to command a fee of around £12.4 million.
The 26-year-old signed a new contract at Porto in February, with his previous deal running out at the end of this season, but that appeared only to be a measure to preserve his transfer value.