Angela Merkel has pushed back against Donald Trump’s extraordinary tirade against Germany on the first day of the Nato summit in Brussels, denying her country was “totally controlled” by Russia and saying it made its own independent decisions and policies.

In less blunt language than the US president’s, the German chancellor made the point that she needed no lessons in dealing with authoritarian regimes, recalling she had been brought up in East Germany when it had been part of the Soviet Union’s sphere of influence.

Arriving at Nato headquarters only hours after Trump singled out Germany for criticism, Merkel said: “I have experienced myself how a part of Germany was controlled by the Soviet Union. I am very happy that today we are united in freedom, the Federal Republic of Germany. Because of that we can say that we can make our independent policies and make independent decisions. That is very good, especially for people in eastern Germany.”

She also hit back at Trump’s criticism that Germany contributed too little to European defence. “Germany does a lot for Nato,” she said.

“Germany is the second largest provider of troops, the largest part of our military capacity is offered to Nato and until today we have a strong engagement towards Afghanistan. In that we also defend the interests of the United States.”

Earlier the US president had accused Berlin of being a “a captive of the Russians” because of its dependence on energy supplies.

At his first meeting of the summit, with the Nato secretary general, Jens Stoltenberg, Trump described the relationship between Germany and Russiaas “inappropriate”.

Nato officials had been nervously awaiting the first meeting as an indicator of how Trump – who arrived in Brussels on Tuesday night – would behave over the next two days. Within minutes they had their answer.

This summit is shaping up to be the most divisive in Nato’s 69-year history. Normally, Nato summits are mostly fixed in advance and proceed in an orderly fashion. Trump’s first words signalled this one was not going to be like that.

He complained that German politicians had been working for Russian energy companies after leaving politics and said this too was inappropriate. Germany was totally controlled by Russia, Trump said.

With Stoltenberg looking on uncomfortably throughout, the US president was unrelenting. “I think it is very sad when Germany makes a massive oil and gas deal with Russia,” Trump said. “We are supposed to be guarding against Russia, and Germany goes out and pays billions and billions dollars a year to Russia.

“We are protecting Germany, we are protecting France, we are protecting all of these countries and then numerous of the countries go out and make a pipeline deal with Russia where they are paying billions of dollars into the coffers of Russia. I think that is very inappropriate.”

He added: “It should never have been allowed to happen. Germany is totally controlled by Russia because they will be getting 60-70% of their energy from Russia and a new pipeline.

“You tell me if that’s appropriate because I think it’s not. On top of that Germany is just paying just a little bit over 1% [of GDP on Nato defence contributions] whereas the United States is paying 4.2% of a much larger GDP. So I think that’s inappropriate also.”

His comments were linked to his push for other European countries – particularly Germany – to pay more for Nato’s defence needs.

“I think it is unfair,” Trump said. Other US presidents had raised the matter of European defence spending levels in the past but he was intent on dealing with it, he continued. “We can’t put up with it.”

The Guardian view on the Nato summit: Europe must come together

Stoltenberg seemed surprised by the force of Trump’s remarks. He attempted to respond, saying mildly: “Even during the cold war, Nato allies were trading with Russia.”

Asked about Trump afterwards, he responded diplomatically, restricting himself to saying the US president’s language had been “direct” and “frank”.

Merkel and Trump have a one-to-one meeting scheduled for later on Wednesday. According to reports in the US media, Trump is keen to see Merkel replaced as chancellor. His outburst could be part of a strategy to try to undermine her at a time when she is domestically vulnerable.

Merkel has been one of the most outspoken critics of Trump among European leaders. The two clashed at the G7 summit in Canada last month. That summit ended in disarray and a spat between Trump and Justin Trudeau, the Canadian prime minister. Nato officials are clinging to hopes that the Nato summit will not end the same way.

Trump’s antagonism towards Merkel is partly personal, a reaction to a senior European politician standing up to him and her very evident dislike of him, which she makes little attempt to hide.

But it is also strategic: Trump resents Germany’s decision to pay much less than the US, UK or France, viewing it as allowing the country to spend more on welfare, health and in other areas. As he said in Brussels, he regards the US as subsidising German spending in popular domestic areas.

Sign up for Guardian Today US edition: the day's must-reads sent directly to you

He also sees the money saved on defence being used to help Germany’s export drive, giving an edge in trade at the US’s expense.

The friction between the two is a long way from 2013 when Trump tweeted praise for Merkel. “Angela Merkel is doing a fantastic job as the Chancellor of Germany,” he tweeted. Youth unemployment is at a record low & she has a budget surplus.”

Trump’s criticism of a German deal with Russia on energy appeared to relate to the Nord Stream 2 pipeline direct to Germany.

Just before he and Stoltenberg sat down to breakfast on Wednesday, Trump claimed the US was paying a disproportionate share of European defence and this was unfair to the US taxpayer.

Europe would have to step up, he said. “They will spend more. I have great confidence they’ll be spending more.”