LONDON — Hundreds of Twitter accounts have been hijacked amid the ongoing diplomatic feud between Turkey and two European nations, Germany and the Netherlands.

It’s not clear how many accounts were taken over altogether but a slew of them, ranging from celebrities to government agencies, suddenly began issuing anti-German and anti-Dutch abuse in Turkish late Tuesday.

“This is a small Ottoman slap,” the swastika-studded messages read in part, blasting “Nazi Germany” and “Nazi Holland.”

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Along with the swastikas and hashtags, the tweets also included a video of Turkish President Recep Tayyip Erdogan making a speech, CNET reports.

The online onslaught came just ahead of Wednesday’s national election in the Netherlands, in which the anti-Islamic, anti-immigrant Party of Freedom led by Geert Wilders was expected to make a strong showing. The vote is considered a test of growing nationalist sentiment across Europe.

The Twitter hijackings also come amid escalating tensions between Turkey and its European partners. Politicians from Turkey’s ruling party have demanded to campaign in Europe ahead of their country’s constitutional referendum next month. The demands have met with refusals and controversy, a display mirrored online by a campaign of low-level web defacements.

Amid a simmering dispute between Turkey and the Netherlands, demonstrators scuffled with Dutch riot police outside the Turkish consulate in Rotterdam, the Netherlands, in March 2017. REUTERS/Yves Herman

Forbes, UNICEF, Duke University, Amnesty International and Starbucks Argentina were among those who appear to have had their Twitter accounts hijacked late Tuesday. Tennis star Boris Becker and the official account of soccer club Borussia Dortmund were also taken over, according to German news agency dpa.

“My twitter account was hacked !!!” Becker said in a follow-up tweet. “I never posted this as I obviously don’t speak Turkish...”

My twitter account was hacked !!! I never posted this as I obviously don't speak Turkish.... pic.twitter.com/G7pNuH1UFj — Boris Becker (@TheBorisBecker) March 15, 2017

Most if not all of the high-profile accounts appear to have since returned to normal.

The mass hijack appears to have been the result of a weakness in a third-party social media management program, Twitter Counter, which is based out of Amsterdam. Twitter Counter CEO Omer Gidor said in an email that the company was investigating the matter.

“We’ve already taken measures to contain such abuse of our users’ accounts, assuming it is indeed done using our system,” he said in an email. Neither he nor Twitter could say how many people were affected.

Twitter Counter also noted that although the company accesses Twitter accounts, it doesn’t store user passwords or credit card information, CNET reports.

Security experts said that the hijack showed the danger of handing over social media accounts to third parties, a move typically taken by companies juggling several personas online.

“Users should be wary as to which services they allow access to write to their Twitter accounts,” said Javid Malik of San Mateo, California-based AlienVault.

It’s not clear who is behind the latest round of hijackings.

A Turkish group calling itself Private Hackers, who’ve claimed responsibility for the earlier defacement campaign, has so far not returned emails from The Associated Press. A number listed by the group in its internet registry records appeared to be out of service.