More CCTV cameras would also be installed in cities and major towns to curb crime, he added.
Inadequate security has been blamed for the authorities' failure to defeat the militant Islamist group Boko Haram.
Last week, President Buhari gave his security commanders three months to defeat the insurgents.
The police are part of the national task force fighting the insurgents in the north-east of the country.
Although the militants have lost their strongholds this year, they are still active and there has been an upsurge in suicide attacks since Mr Buhari took office.
The bombers often target markets and bus stations.
A senior officer told the BBC that the police force had an estimated 375,000 officers at the moment.