Authorities have arrested three of the four men that allegedly robbed a bank in Thessalonki on Friday in what is believed to be one of the biggest holdups to take place in Greece, police said on Saturday.

Two men include a 57-year-old man caught in an area close to Florina, near the northern border with the Former Yugoslav Republic of Macedonia (FYROM), and a bank employee, aged 45.

The bank employee, who claims to have a severe heart problem, is under police guard at a hospital in Thessaloniki.

The third suspect, an off-duty police officer, was arrested on Friday as he attempted to escape after the bank heist in which 2.8 million euros in cash was taken from an Alpha Bank cash-distribution center.

The gang had tied up two security guards and fired shots into the air during the robbery.

Police have launched a manhunt for a fourth suspect, aged 28.

Authorities recovered 98,000 euros of the stolen money which they said was found with the 57-year-old suspect.