It's called "the Singing Sailor", and it has just been lowered into the sea in the archipelago near Stockholm. It is a waterproof box about a metre high, containing a neon sign with a sailor in his underpants, above the message "Welcome to Sweden – Gay since 1944".

The box also contains a sonar system that transmits – in Morse code – "This way if you are gay".

Sweden legalised homosexuality in 1944. Russia, however, is a country of institutionalised homophobia. Recent new laws banned gay "propaganda" and anti-gay vigilantes and hate crimes are barely discouraged.

Though homosexuality has been decriminalised since 1993, the Kremlin and its Orthodox church allies have increasingly painted gay culture as undesirable evidence of Western decadence.

The Singing Sailor is a joke with a serious point – not only about Russian oppression, but on the home front as well.

The Swedish Peace and Arbitration Society, which was behind the stunt, said its purpose was to urge the Swedish government "to think in new ways instead of falling back on territorial defence, conscription and rearmament – the world doesn't need any more weapons".

"If military actions and weapons had functioned as conflict-resolution methods, there would be peace in the world a long time ago," SPAS president Anna Ek said.

In September last year, two Russian fighter bombers reportedly entered Swedish airspace, prompting fury from the locals, and the next month the Swedish military claimed a foreign submarine had been patrolling Swedish waters.

In April this year, Finland fired a depth charge in a warning to a suspected submarine in its waters near Helsinki.

Last month, Swedish security police listed Russia as the biggest security threat to the country.

Last Friday, Sweden and its Nordic neighbours announced a new plan to extend military cooperation in response to increased Russian military activity.

Neither Sweden nor Finland are NATO members.

The defence ministers of Sweden, Norway, Denmark, Finland and Iceland signed a statement agreeing to share defence intelligence and plan new joint military exercises.

"The Russian aggression against Ukraine and the illegal annexation of Crimea are violations of international law and other international agreements," the statement said. "Russia's conduct represents the gravest challenge to European security."

"The Russian military acts in a provocative manner along our borders and there have been several border violations around the Baltic countries. Russian propaganda and political manoeuvring contributes to sowing discord between the countries and inside organisations such as NATO and the European Union."

A new report, written partly by Russian politician Boris Nemstov and completed by his colleagues after he was murdered, claims that hundreds of Russian soldiers have died fighting covertly in Ukraine.

At least 70 died this year in the fierce battles around Debaltseve, which resulted in a rout of Ukrainian forces and the restoration of a vital supply line for separatist fighters, the report claims.

Another 150 died in eastern Ukraine last August, alongside separatists fighting to rebuff an advance by Ukrainian government forces.

And the report says there are currently up to 10,000 Russian soldiers still in eastern Ukraine supporting the separatists, despite the current Minsk ceasefire accord, which is looking increasingly shaky.

The report, titled Putin. War., was released on Tuesday. It was based partly on interviews with families of Russian troops, Nemtsov's allies said.

The report claims separatist leaders in Ukraine are controlled by Vladislav Surkov, an aide to Russian President Vladimir Putin, Radio Free Europe reported.

A spokesman for the Kremlin declined to comment on the report, saying he was not familiar with it and could not say if Mr Putin would look into it.

Nemtsov, a former deputy prime minister who became a fierce critic of the Putin regime, was shot dead in February, metres from the Kremlin walls.

He left behind materials including a table of contents, handwritten notes and other documents, which were compiled into the final report by writers including economists Sergei Aleksashenko and Alfred Koch, and journalists Aider Muzhdabayev and Oleg Kashin.

"I know what needs to be done," Nemtsov is quoted saying in the report. "We need to write a report 'Putin. War.', publish it in large numbers and hand it out on the streets. We will tell how Putin unleashed this war. That's the only way to defeat propaganda."

However the report's authors struggled to find a printer who will distribute it in Russia on a large scale.

The report said last year Russian soldiers' families were given 2 million rubles each ($45,000) after signing pledges not to reveal where their loved ones died.

However, the report claimed that Russia had started discharging troops from the army on paper before sending them into Ukraine – then refusing to pay compensation to their families.

"The most important thing is to tell the truth," activist Ilya Yashin said at the report's launch in Moscow, Radio Free Europe reported. 
"The purpose of this report is to tell people the truth. The leadership of our country bears responsibility for a crime. It bears responsibility for an enterprise that has victimised Ukrainian citizens and our fellow Russian citizens."