Getty Germany says Hungary’s use of tear gas is ‘not acceptable’ Budapest has failed to treat refugees with decency, says German defense minister.

Hungary used a water canon and tear gas to drive asylum seekers back from the Hungarian-Serbian border on Wednesday, triggering international criticism of their handling of the migration crisis.

"This is not acceptable and this is against the European rules that we have. Therefore it is very important that we stick to the respect [where] human dignity and human rights are concerned," said Ursula von Der Leyen, Germany's defense minister.

“The refugees have a right to be treated decent. This is something where we really have a lot to discuss in Europe," she told CNN on Wednesday.

Von Der Leyen’s German Christian Democratic Union (CDU) party and the ruling party in Hungary, Fidesz, are both members of the center-right European People’s Party (EPP).

United Nations Secretary General Ban Ki-moon said earlier on Wednesday that he was "shocked" by the treatment of migrants.

Guy Verhofstadt, the leader of the liberal ALDE group in the European Parliament, called the recent events in Hungary a "shame" during the Parliament’s debate on migration.

Earlier on Wednesday, the European Commission said that migration commissioner Dimitris Avramopoulos will assess the situation in Hungary upon his return to Brussels on Thursday. Avramopoulos has been in Budapest.

Hungary has refused to allow asylum seekers to enter the country and has shut down all access from Serbia by building a fence. Hungarian police on Tuesday said they had arrested 60 people accused of trying to breach the razor-wire fence.

In Horgoš, just over the Serbian border, several hundreds of people are stranded. “The refugees we’ve spoken to have described the uncertainty and indignation they feel, stuck in limbo with a complete lack of information,” said Tirana Hassan, director of crisis response at Amnesty International, the human rights NGO. “They are effectively stuck in a no-man’s land on the Serbian border and the Hungarian border fence.”

Many of the migrants have been traveling from Greece through Serbia and Hungary, hoping to reach Germany. According to the Hungarian authorities, around 9,000 people crossed into the country before the border was closed on Monday.

Maïa de La Baume contributed to this article.