MOSCOW: A Russian opposition activist who committed suicide at a Dutch deportation center after his request for political asylum was turned down was laid to rest Wednesday, as fellow activists demanded answers from the Netherlands over the murky circumstances of his death.

Alexander Dolmatov, a 36-year-old rocket engineer who feared arrest in Russia after an opposition protest turned violent in May, was taken to the prison-like deportation center in Rotterdam on the night of Jan. 16. The next morning he was found dead in his cell.

Dutch authorities are investigating and have not released an official cause of death, but his background in missiles and an enigmatic suicide note have fueled speculation about the case.

Fellow activists from The Other Russia, a punkish and anti-globalist opposition party with a cultish devotion to their leader, novelist Eduard Limonov, and other critics are pointing to Dutch immigration officials as the ones at fault and saying Dolmatov never should have been in detention.

A few dozen, dark-jacketed members came to pay their respects at the Moscow wake, where Limonov said he would "demand an investigation into what happened, because there are a lot of absolutely improbable circumstances coming up."

Dolmatov fled to the Netherlands believing he would quickly earn refugee status given concern in the West over a Kremlin crackdown on the opposition, his friends have been quoted as saying. Already, one participant in the May protest, which took place on the eve of President Vladimir Putin's inauguration for a third term, has been sentenced to 4 1/2 years in prison and about a dozen others are awaiting trial.

Dolmatov reported coming under pressure from Russia's security service, whose agents he claimed had threatened to get him fired from his job at a military plant. Immediately after he left for the Netherlands, the apartment where he lived with his mother was searched by police.

But Russian prosecutors did not file charges against him, and Dutch authorities denied his asylum request on Dec. 14.

Conspiracy theories about his death have spread across the Russian blogosphere. Opposition activists and bloggers have claimed his work designing missiles attracted the attention of Dutch security services, even though Dolmatov had the lowest possible clearance. Dolmatov himself had accused the Russian security services of trying to recruit him in 2008 and 2011.

Confusion deepened when Russian media published his suicide note. In a hastily scribbled letter to his mother, Dolmatov wrote that he was killing himself "so as not to return as a traitor, having shamed everyone" because he had "betrayed an honest person, betrayed the security of our Motherland."

Questions loom over the last few weeks of his life. His mother said she had increasing trouble reaching him on the phone and at one point he went missing for five days.

"He was in a strange state of drowsiness," his mother, Lyudmila Doronina, said Wednesday. "I once got through to him, he said, 'I'm sleeping, I want to sleep,' and it had never been like that. I understood something had gone wrong, and then it was all over."

His lawyer, Marq Wijngaarden, had filed an appeal on Jan. 11, which would have allowed him to remain in the Netherlands for at least a few more months. But it is unclear whether Dolmatov was aware of it.

Saskia Bolt from the Dutch Council of Refugees said the main issue was why the Russian asylum seeker was in detention if his case was still running.

More than half of Russian applications for asylum are rejected in the Netherlands, according to government data. In 2011, the last year for which the figures are available, 494 Russians sought asylum.