Suppress = to end something by force;  prevent from being known or seen

• The government suppressed the pro-democracy movements by lathi-charge and arrests.
• They could not suppress the rebellion by force.
• She suppressed her feelings for the sake of peace.
• He managed to suppress his irritation.

Oppress = 1.  rule people unjustly or cruelly

• For years people of Uganda were oppressed by the ruthless dictator Idi Ameen.
• Oppressive laws and rules.
• A cruel tendency to oppress racial minorities.
• Years of violence and oppression.

Oppress = 2. cause to feel troubled or uncomfortable

• Oppressive weather/heat.
• The strange dream about his gloomy future oppressed him.