European leaders reacted with restraint and concern Monday to the narrow outcome of a referendum in Turkey that grants sweeping new powers to the nation's president.

While relations between the European Union and Turkey have been deteriorating for months, the result of the Turkish vote will likely only widen the growing political and cultural distance between the 28-nation bloc and the EU candidate country.

Both Germany and France expressed concern about possible election irregularities and called on Turkish President Recep Tayyip Erdogan to engage in dialogue with the opposition after Sunday's referendum's showed how deeply the country is divided.

"The narrow result of the vote shows how deeply split the Turkish society is," German Chancellor Angela Merkel and Foreign Minister Sigmar Gabriel said in a joint statement. "This implies a big responsibility for the Turkish government and President Erdogan personally."

About 51.4 percent of Turkish voters cast their ballot in favor of Erdogan's long-time plans to greatly expand the powers of his office, while the "no" vote saw 48.6 percent support, according to state-run Anadolu Agency.

The margin fell short of the sweeping victory the 63-year-old Erdogan had sought in the referendum. Nevertheless, it could cement his hold on power in Turkey for a decade and is expected to have a huge effect on the country's long-term political future and its international relations.

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Several Turkish opposition groups claimed irregularities during the voting process and the Organization for Security and Cooperation in Europe said that the referendum fell short of international standards.

Merkel and Gabriel said that Turkey — as an OSCE member and EU candidate country — needs to consider these concerns.

French President Francois Hollande also warned that if Turkey reinstates the death penalty, as Erdogan suggested in a speech late Sunday, it would "constitute a rupture" with Turkey's pledges to respect human rights as part of efforts to join European institutions.

Austrian Foreign Minister Sebastian Kurz said Sunday that the referendum was bound to complicate further cooperation between Ankara and the EU. Kurz tweeted that the result "shows how divided the country is. Cooperation with #EU will become even more complex."

Kati Piri, a member of the European Parliament and parliamentary rapporteur on Turkey, struck a more conciliatory tone.

"Outcome shows millions of Turkish citizens share same European values," Piri tweeted. "The EU should never close door to them."

However, the overwhelmingly subdued and critical reactions by European leaders were a reflection of how complicated and icy relations between the bloc and Turkey have become over the past year — just when the EU is looking to Turkey for its support in the fight against the Islamic State and in helping slow and regulate the flow of migrants into Europe.

The Europeans also need Turkey as a vital and reliable partner in the NATO, but there too have been problems, after Turkey temporarily banned German lawmakers from visiting German army personnel on a military base in Turkey in the past.

Further tensions arose last month, when Turkish officials' attempts to rally support among their citizens living in Europe for the referendum caused irritation and several of their public events were canceled. That caused Erdogan to accuse German and Dutch officials of acting like Nazis which, in turn, prompted strong condemnation of the Turkish president's words from European leaders.

Erdogan himself struck a defensive note after the referendum saying "we want other countries and organizations to show respect to the decision of our people."

In a speech Monday, he sounded even more defiant saying, "we have put up a fight against the powerful nations of the world ... We did not succumb. As a nation we stood strong."

While most Europeans were never enthusiastic about Turkey's bid to join the EU and membership negotiations have made little progress over the past decade, the prospect of Turkey joining the bloc, it seems, have become more unrealistic than ever before.

"The impact of this referendum in terms of Turkey's democratic credentials on the world stage is unfortunately negative," said Marc Pierini, an expert with the Carnegie Europe think tank. "Both the unfair campaign and the substantive reforms that will now be implemented take Turkey away from the prospect of a political alliance with the EU."

"However, this new state of affairs may suit both president Erdogan and EU leaders," Pierini added.

Despite all these problems, Gabriel said that the EU needs to keep up its dialogue with Turkey.

The German foreign minister, talking to reporters in Tirana, Albania, said that Brussels should intensively work to find channels of dialogue on "how to impact so that Turkey remains a democratic country."