Now in the third year of war, the challenges that Ferrexpo face cannot be understated. Our people and our business continue to be affected by war. Our strategy to move early and right-size our business is, however, working. We have learned to be more nimble and how to adapt and respond to ever-changing circumstances. We continue to work tirelessly to protect our people, preserve the integrity of our assets, and contribute to local communities and the national economy. In the face of such extraordinary circumstances, it is pleasing that we can report production and sales that met logistics capacity available to us as we continue to export to Europe and beyond. During the year, we also invested in our operations, sticking to our CapEx programs that can deliver short-term efficiencies and improvements in product quality.
The determination of our workforce has allowed us to perform exceptionally well, and we are proud of these achievements.
The safety and well-being of our people remains paramount, especially during a time of war. As a result of logistics constraints imposed on us by the war, we operated at a reduced capacity during 2023, but we still managed to maintain a full workforce by placing some people on furlough or reducing shift durations. Maintaining our workforce has proven the right strategy as we move into 2024, as we start to recommission production as logistics constraints ease. At the present time, some 641 of our colleagues are serving in the Armed Forces of Ukraine, and we continue to support them on an ongoing basis with safety equipment, clothing, and other essentials. It is with deep sadness that we must still report that 35 colleagues have lost their lives while serving since the start of the war in February 2022.
On a brighter note, during 2023, 67 colleagues returned from the armed forces, the majority of whom have now gone back to the workplace. They are joined by over 100 new colleagues who settled in our communities after fleeing to the Poltava region from the eastern parts of Ukraine. The spirit and determination with which our colleagues come to work day in, day out, is a testimony to the resilience of Ferrexpo, our local communities, and to Ukraine.
The strength of our people and the strategy to right-size our business has ensured that our operations remained cash positive during a time of war, allowing for continued controlled investment whilst maintaining a stable net cash position. On sales of 4.2 million tons of premium iron ore and concentrates at iron ore prices that bucked market pessimism, we generated revenues of $652 million. Our cost of sales on a unit basis fell 8% to $76.5 per ton. This was in part due to lower gas and diesel prices, though can also be attributed to efficiency gains and cost-saving measures.
After positive cash flows from operating activities of $101 million, we were able to report an underlying EBITDA of $130 million, all while investing over $100 million during the year, and ending with a net cash of $108 million, slightly higher than the previous year. In 2024, we will continue to work hard, protect our people. We are strong. Our nation is strong. Slava Ukraini!