The vehicle was traveling from the northern town of Kukes to the capital Tirana. Some 30 passengers were on board, including women and children, when it left Kukes.
Leshja said the gunmen later used an automatic weapon and at least one grenade against police at a roadblock set up to halt the bus. The two gunmen were later arrested.
The three people who were seriously wounded, including one of the captured gunmen, were flown by helicopter to a hospital.
(AFP, Reuters, AP, dpa)