The incident took place near one of the famous hotels at Al-Bahr street in Al-Arish city, they said.
The roadside bomb went off and hit an armored vehicle carrying police personnel.
Three officers, three conscripts and three civilians suffered injuries, they added.
Ambulances and security officials rushed to the site of the incident and transferred the injured and cordoned the area.
The officials said that the attackers belonged to the Sinai-based militant group Ansar Biet el-Maqdes.
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North Sinai has witnessed many terrorist attacks since the January 2011 revolution that toppled ex-president Hosni Mubarak.
The attacks, mainly targeting police and military, increased after the ouster of Islamist ex-president Mohamed Morsi in 2013 by military following massive protests against his rule.
The military has launched security campaigns in the area, arrested suspects and demolished houses that belong to terrorists, including those facilitating tunnels leading to the Gaza Strip.