At a victory rally in Ankara, the president praised his supporters for "standing tall", in the face of what he dubbed the "crusader mentality" of Western countries.
Representatives from a coalition of worldwide bodies said the vote took place on an "unlevel playing field", with the "yes" campaign dominating media coverage. "All debates about the constitutional referendum are now over", he said.
The cabinet said it hoped the vote would contribute to "more development success across the country".
Monitors from the Council of Europe said that journalists seen as hostile to the referendum had been jailed, while unfriendly media outlets were closed by the Erdogan government.
"Turkey's mainly Kurdish southeast and its three main cities, including the capital Ankara and the largest city Istanbul, looked set to vote No, after a bitter and divisive campaign, " a local newspaper reported on Sunday. The main opposition party has demanded the result be nullified, saying the voting was marred by irregularities.
The opposition has been particularly incensed by a last-minute move from the YSK to accept ballot documents in envelopes without an official stamp, as required by Turkish law. "This means a great responsibility for the Turkish leaders and for President Erdogan personally", she said as the Turkish head of state conducted a violent verbal campaign against German leaders after the ban on pro-Erdogan meetings in Germany.
The State Department was far less enthusiastic about the outcome of the referendum.
Erdogan said that a huge number of Turkish voters took part in the referendum.
It's unclear what exactly Trump was congratulating Erdogan on other than simply winning, which is his favorite thing.
Global monitors from the joint mission of the OSCE Office for Democratic Institutions and Human Rights and the Parliamentary Assembly of the Council of Europe said media coverage during the referendum campaign resulted in an "unlevel playing field".
And the U.S. State Department released a statement Monday urging the Turkish government to "protect the fundamental rights and freedoms of all its citizens-regardless of their vote on April 16-as guaranteed by the Turkish Constitution and in accordance with Turkey's global commitments, such as under the Helsinki Charter", which requires signatory countries to uphold human rights.