A large number of Twitter accounts, including international aid organizations, news agencies and political entities, have seemingly been hacked by a group supporting the Turkish government.

The tweets include a swastika, as well as the hashtags ‘Nazialmanya’ (NaziGermany) and and ‘Nazihollanda’ (NaziHolland), presumabley referring to the increasing diplomatic tension between Holland and Turkey.

“See you on April 16," the tweets read, which is the date of Turkey’s referendum to grant more powers to Erdogan, while also referring to the hack being a “little Ottoman slap."

The tweets also link to a YouTube video uploaded on March 14, which includes a number of clips of Turkish president Recep Tayyip Erdogan.

READ MORE:Turkey's Erdogan calls Netherlands 'rotten, terrorist state'

It’s unclear at this stage who is behind the hack or exactly how many accounts have been affected. According to Bloomberg, Reuters Japan, Forbes, BBC North America and German newspaper Die Welt were spammed, as well as accounts associated with the Mayor of Bordeaux, Alain Juppe, Sprint CEO Marcelo Claure and the European Parliament.

RT’s Spanish account was also hacked.

'Hackean' el Twitter de RT en Español y otros medios con declaraciones antieuropeas de Erdogan https://t.co/L1l2bWk0EEpic.twitter.com/3f3PhAMCf0 — RT en Español (@ActualidadRT) March 15, 2017

A Twitter spokesperson said they “are aware of an issue affecting a number of account holders this morning.”

The company “quickly located the source which was limited to [a] third party app” and “removed its permissions immediately.”

It’s understood that third party service Twitter Counter – which allows Twitter users to track stats, followers and hashtags – has been hacked and the accounts of its users spammed.

Twitter Counter tweeted that an investigation in underway.

“We're aware that our service was hacked and have started an investigation into the matter,” it said. “We've already taken measures to contain such abuse.”

We're aware that our service was hacked and have started an investigation into the matter.We've already taken measures to contain such abuse — TheCounter (@thecounter) March 15, 2017

“One thing is important to note – we do not store users’ Twitter account credentials (passwords) nor credit card information,” it added.

One thing is important to note - we do not store users’ Twitter account credentials (passwords) nor credit card information. — TheCounter (@thecounter) March 15, 2017

So twitter counter is the service that got hacked which is why everyone is tweeting swastikas pic.twitter.com/ty68jLPUBB — fake news lover (@dannolan) March 15, 2017

In November, a number of accounts including those of PlayStation, The New Yorker, Lionel Messi, Microsoft Xbox and the Red Cross were hacked with tweets advertising ways to garner more followers. The tweets had been posted via Twitter Counter, Engadget reported. About 2 million users were said to have been affected.

We can confirm that our service has been hacked; allowing posts on behalf of our users! We have launched an investigation into this matter. — TheCounter (@thecounter) November 19, 2016

A number of accounts said to have been hacked have since regained control of their accounts and deleted the tweets. BBC North America tweeted, “Hi everyone – we temporarily lost control of this account, but normal service has resumed. Thanks.”

Hi everyone - we temporarily lost control of this account, but normal service has resumed. Thanks. — BBC North America (@BBCNorthAmerica) March 15, 2017

Twitter Counter owner Boris Veldhuijzen van Zanten confirmed to Engadget that Twitter Counter is working to resolve the issue. The tweets appear to have stopped, although many remain on the hacked accounts.