CAIRO — Thousands of Egyptians marched on the city of Port Said’s investment zone in a second day of demonstrations, as the army was deployed to protect businesses.

The marchers are calling for a strike in the Suez Canal city, to protest against death sentences handed down last month against 21 people for their role in the nation’s worst ever soccer riot a year earlier.

While the unrest hasn’t affected canal operations, it underscores the challenges confronting President Mohammed Morsi as his government tries to revive an economy that stalled in the two years since Hosni Mubarak’s ouster.

The currency has hit record lows, unemployment has risen and a $4.8 billion International Monetary Fund loan has been repeatedly delayed.

The marchers chanted “Leave, Morsi,” Ramy Rasmy, one of the protesters, said by phone from the demonstration. The military deployed troops in the free zone to prevent damage and violence, Sameh Abdel-Khaleq, an employee at one of the affected factories, said by phone from Port Said.

More than two dozen factories in the industrial zone were closed today and government workers were sent home amid growing security concerns. Yesterday, demonstrations forced the evacuation of the Suez Canal authority’s building and brought work across the city largely to a standstill.

Violence late last month in Port Said and two other canal cities left more than 30 people dead and prompted Morsi to enact emergency measures and a curfew in the areas.