Two policemen were also wounded in the attack on the road between North Sinai provincial capital El-Arish and the town of Rafah on the Gaza border, the interior ministry said.
"An explosive device went off near one of the APCs [armoured personnel carriers] of a joint police and army security convoy on the road between El-Arish and Rafah, killing six policemen including an officer and wounding two others", the ministry said in a statement.
It said security forces had cordoned off the area and an investigation was being carried out.
The attack has not been claimed but the Sinai Peninsula is a hotbed of jihadist groups who regularly attack security forces in retaliation for a government crackdown against Islamist supporters of ousted president Mohammed Morsi.