ISTANBUL — Nationalist and pro-government throngs filled the streets of Istanbul and Ankara for two nights last week, chanting “God is great” as they stormed a prominent newspaper and set fire to the offices of a Kurdish political party.

Turkey’s economy, long an emerging market darling, has cooled, and the value of the Turkish lira slips by the day. Cruise ships have stopped docking in Istanbul, and many residents avoid the subway because of bomb threats.

A sense of unease is spreading in Turkey as the decades-old conflict flares between Kurdish militants and Turkish security forces in the volatile southeast. Fears are growing that the country could return to the dark days of the 1990s, when the conflict was at its height.

The upheaval in major cities has prompted Turks, especially Kurds, to share pictures on social media comparing their own cities to ravaged areas in Syria.