(Adds quotes from German foreign minister)
By Ralph Boulton and Andrea Shalal
ISTANBUL/BERLIN, March 4 (Reuters) - Turkey said on Saturday it would keep holding rallies in Germany and the Netherlands to urge Turks living there to back a vote to boost President Tayyip Erdogan's powers, despite opposition from authorities in both countries.
Foreign Minister Mevlut Cavusoglu criticised German and Dutch restrictions on such gatherings as undemocratic, and said Turkey would press on with them in the run-up to the April 16 referendum.
"None of you can prevent us," he told a campaign event in southern Turkey. "We can go anywhere we want, meet our citizens, hold our meetings."
The defiant Turkish comments highlight the importance Erdogan places on securing the new powers, especially since a failed military coup last July, in what could turn out to be a close vote.
The disagreement has led to sharp exchanges between the North Atlantic Treaty Organization partners. Adding to the tensions, Germany has demanded the release of a German journalist arrested in Turkey on Monday, while Erdogan on Friday called him a "German agent."
Chancellor Angela Merkel spoke by phone on Saturday with Turkish Prime Minister Binali Yildirim, a German government spokesman said, without providing details of the conversation.
German Foreign Minister Sigmar Gabriel, who will meet with his Turkish counterpart in Berlin this week, warned against stirring up tensions between the two countries, but also said Berlin would not refrain from criticism where warranted.
"The German-Turkish friendship runs deeper than the diplomatic tensions we are experiencing today," he wrote in an essay published in the Bild am Sonntag newspaper on Sunday. "We cannot allow hate and misunderstanding to grow out of political differences."
Gabriel said Turkish politicians who wanted to campaign in Germany should respect the "rules of law, as well as decency."
Several members of Merkel's coalition voiced concerns on Saturday about Turkish politicians rallying support among Germany's 1.5 million Turkish citizens.
Juergen Hardt, foreign policy spokesman for her conservative Christian Democratic Union, told Reuters: "We don't want marketing for the undemocratic and illegitimate Turkish referendum on German soil."
Several events have already been blocked for security reasons, sparking anger among Turkish leaders who accused Germany of a double standard.
Turkish Economy Minister Nihat Zeybekci has had two events cancelled, but plans to speak at events on Sunday in Leverkusen and Cologne in the state of North Rhine-Westphalia (NRW), which has a large Turkish population.
The state premier of NRW and local politicians want the federal government to provide guidance about such campaign events, something that Merkel and Gabriel would like to avoid as they struggle to balance the broader issues at hand with Turkey, including migration and the fight against Islamic militancy.
Critics of Erdogan fear the proposed new powers, including freedoms to govern by executive orders, would entrench autocratic trends. Erdogan says they are vital in tackling Kurdish rebels, Islamist militants and other political enemies in a land with a history of unstable coalition governments.
The Dutch government said on Friday it would inform Ankara of its opposition to "undesirable" proposals to hold a referendum rally in Rotterdam.
"The Netherlands told us 'You can't campaign in our public spaces.' What do you mean, we can't? Where is democracy ... where is freedom of expression?" Cavusoglu said.
(Reporting by Ralph Boulton, Andreas Rinke, Gernot Heller, Reuters TV and Andrea Shalal; Editing by Mark Trevelyan and Richard Chang)