An Italian Red Cross aid worker held hostage by Islamic militants is in pain and unable to walk after more than three months in captivity in Sulu province, the military said Wednesday.

Eugenio Vagni, 62, has previously been reported by the authorities as needing surgery for hernia, with Jolo island's harsh terrain also said to be taking a toll on his emotional state.

Abu Sayyaf militants seized Vagni and two other International Committee of the Red Cross (ICRC) workers in January. The Filipina hostage was released on April 2 while the Swiss captive walked free Saturday.

Latest intelligence reports indicated that Vagni could no longer walk because of his condition, military spokesman Lieutenant Colonel Edgar Arevalo said in a statement Wednesday.

He said troops were continuing to apply "calibrated pressure" against Abu Sayyaf, which has splintered into three groups in a bid to confuse the authorities.

"Reports say he is well but unable to walk due to hernia," Arevalo said of Vagni.

"Aside from the calibrated pressure to deny the bandits freedom of movement, the kidnappers are saddled with the fact that Vagni is not ambulant and must be carried as they move," Arevalo said.

He said Vagni was "alive but under tight guard."

Vagni was seized by Abu Sayyaf militants along with ICRC colleagues Andreas Notter of Switzerland and Mary Jean Lacaba of the Philippines. Notter flew back to Switzerland Tuesday.

Numbering in the low hundreds, the Abu Sayyaf was founded in the 1990s ostensibly to fight for an independent Islamic state. The group later branched off into high-profile abductions and bombings.