Soldiers were manning checkpoints on all access roads to the capital and outside key state institutions, local media reported.
The police and army were toughening security in central Cairo's Tahrir Square, where Islamists and military supporters were planning their rival demonstrations later Sunday.
Barbed wire and barricades blocked traffic to the square as security personnel were deployed with sniffer dogs outside the nearby National Museum.
Metal detectors were also installed at entrances to Tahrir to prevent weapons from being smuggled into the square.