Two swastikas were discovered on the Upper West Side on Thursday morning, one day after the NYPD warned of a "troublesome" uptick in anti-Semitic incidents across the city over the last month.

According to a witness who shared photos with Gothamist, the hate symbols were spray-painted onto a concrete outpost in the Hudson River near 72nd Street. Police arrived around 10:45 a.m., the witness said, as a few people stood around taking photos.

The discovery comes in the wake of the Pittsburgh synagogue massacre, and amid a surge of reported anti-Semitic activity both nationwide and in New York City. On Tuesday night, an unidentified vandal drew several swastikas and racist slurs on a private residence in Brooklyn Heights, according to police. (The NYPD could not immediately confirm Thursday's incident).

During a briefing on Wednesday morning, Chief of Detectives Dermot Shea said police had received a wave of similar reports in recent weeks. "We’ve seen in the last month an increase in anti-Semitic hate crimes, particularly swastikas, on buildings in part of the city," he noted. "In last 28 days particularly, which is a little troublesome, we have seen an uptick in that category."

Data provided by the city shows that there were a total of 142 anti-Semitic hate crimes reported through October 28th of this year—up from 126 in the same period last year, which was almost double the number reported in New York City in 2016. According to the Anti-Defamation League, anti-Semitic incidents soared last year following the deadly white nationalist rally in Charlottesville, in which President Donald Trump praised "the fine people on both sides."

Amid this latest increase in anti-Semitic activity and political violence, the president has continued to amplify baseless conspiracy theories about George Soros, a prominent Jewish progressive and frequent target among far-right anti-Semites, including the alleged Pittsburgh shooter and suspected mail bomber. On Wednesday, Trump told Fox News that he "wouldn't be surprised" if Soros was funding the migrant caravan.

Anyone with information in regards to this incident is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782). The public can also submit their tips by logging onto the Crimestoppers website at WWW.NYPDCRIMESTOPPERS.COM, on Twitter @NYPDTips or by texting their tips to 274637 (CRIMES) then enter TIP577.