German Chancellor Angela Merkel voiced concern after leading Kremlin opponents planning a protest near the summit venue --
including chess legend Garry Kasparov -- were prevented from travelling there by Russian authorities.

"I hope that they will be able to express their opinion," Merkel told a joint news conference at the end of the two-day summit at which EU leaders discussed the state of democracy and human rights.

"I'm somewhat concerned that people had difficulties getting here, but perhaps a possible demonstration can still take place," Merkel said.

"If demonstrators throw stones, if they smash windows, then of course they should be curbed. But if someone has done nothing, if
they just want to go to a demonstration, then it's different," Merkel said.

Russian President Putin testily defended "preventive measures" taken by Russian police ahead of the rally, comparing these to common practice in European countries.

Expressing assurances that the opposition's right to protest would be respected, Putin countered that German authorities have not ruled out using preventative detention in the run-up to next month's Group of Eight (G8) summit in the German resort of Heiligendamm.

"We will not however point the finger at others," the Russian leader said.

In Hamburg alone, German police resorted to water canons and truncheons last week in clashes with some 2,000 activists demonstrating against the upcoming G8 summit on the Baltic Coast.

Boarding hindered

Kasparov's Other Russia movement had planned an anti-Kremlin protest to coincide with the tense meeting between Russian President Vladimir Putin, Chancellor Merkel, the current holder of the European Union's six-month rotating presidency, and European Commission President Jose Manuel Barroso.

The former chess champion had been scheduled to fly to the Volga River city which is 70 kilometers (43 miles) from the summit venue of Volzhsky Utyos.

"Not one member of the Other Russia delegation was allowed to board," Denis Bilunov, a spokeman for Kasparov, told AFP.

The leader of the radical National Bolshevik movement, Eduard Limonov, was also stranded at the Russian capital's Sheremetyevo airport, as were a number of journalists.

Wall Street Journal correspondent Alan Cullison said police had told them that there was a problem with the tickets.

Passports confiscated

A representative of a human rights organization had his passport confiscated. "We're at Sheremetyevo airport and uniformed men have taken our passports. They've taken 13 passports. I consider this a criminal offence," said Lev Ponomaryov of the For Human Rights organization.

"They told us at the check-in that our tickets had been rejected by the computer as they had been sold (to other passengers). But some journalists who were allowed to board told us the plane was half empty."

A presidential spokesman denied the Kremlin was involved in the incident and said he did not expect the incident to be discussed at the summit.

"I don't think the issue of the non-arrival of a Russian citizen, even a famous one will be on the summit agenda," said Dmitry Pescov. "I cannot comment on behalf of the police. The Kremlin was not in Sheremetyevo."

Some "constructive" discussions

Meanwhile, Russian and European leaders vowed to hold frank discussions about all areas of dispute. President Putin said: "We are ready for an open and honest dialogue without any taboo subjects."

Chancellor Merkel said she hoped for firm solutions to the problems between the EU and Russia. "I hope that we can take concrete steps where there are snags and hitches."

Still, participants said "constructive" discussions had taken place at the summit in Volzhsky Utyos (Volga Cliff), a picturesque
resort complex some 1,000 kilometres (620 miles) south of Moscow.

Putin and EU leaders discussed setting up an alert mechanism for
increasingly vital Russian energy supplies to Europe following a
request from Merkel after recent gas and oil cut-offs from Russia.

Putin told Barroso and Merkel over dinner on Thursday that
supply agreements he signed this month with the Central Asian states of Kazakhstan and Turkmenistan would benefit Europe.

Talks touched on Russia's bid to join the World Trade Organisation (WTO), which is being dogged by trade tariff disputes with Brussels, and the future status of the Serbian province of Kosovo.

"Russia can't tango on its own"

But the overall impression was one of deep discord between the two sides.

"We found many problems during the summit. We have not always managed to convince each other but I think it's always better to
speak to each other than to speak about each other," Merkel said.

Negotiations over a partnership agreement between the EU and
Russia, including in the sensitive energy sphere, are being blocked
by EU member Poland because of a trade dispute with Moscow. The current agreement runs out this year and can be extended, but EU officials said that failure to start negotiations would be an embarrassment for both sides.

Barroso on Friday reiterated the EU's position that there was "no basis" for Russia to maintain a ban on Polish meat imports, the
source of the dispute. Russia imposed the ban last year, citing food safety concerns.

Putin responded that the EU should first solve its "internal problems," and Kremlin officials said that Russia had already made sufficient concessions to Poland and was waiting for a response.

"Russia can't tango on its own," said Dmitry Peskov, a Kremlin
spokesman.

The EU's External Relations Commissioner Benita Ferrero-Waldner ascribed some of the frostiness in relations to upcoming parliamentary and presidential elections in Russia.

"Russia is in a pre-election period so maybe nationalistic feelings are coming up. But at the same time there are questions that have to be solved in a constructive spirit," she told reporters.