Martins signed a six-month loan deal with Birmingham just before the transfer window closed on January 31 with an option for a permanent move to the Midlands club, but Rubin coach Kurban Berdyev said he wanted the 26-year-old to return to Russia.
"Martins left Rubin due to personal reasons," Berdyev was quoted as saying by the Daily Mail.
"We agreed that he will stay there until the summer and then return to Kazan."
Martins, who has failed to establish himself as one of the key players for Rubin after joining them from Bundesliga side VfL Wolfsburg last July, showed that he had not lost much of his scoring touch by sweeping home a last-minute winner for Birmingham in a 2-1 upset victory over Arsenal just six minutes after coming on as a substitute in the League Cup Final at Wembley Stadium on Sunday.
Despite his cup heroics Berdyev said Rubin have had no offers for Martins: "We haven't received any formal offers from Birmingham."
Meanwhile, the Russians also denied media reports they had offered Real Madrid 45 million euros for Brazil midfielder Kaka.
"Of course, we've heard these rumours, it's absolutely ridiculous," a club spokesman told Russian media.
Spanish sports daily Marca reported that Rubin had bid for the 28-year-old Kaka, who has been struggling with injuries this season.
