Putin said all of Russia's religions played a valuable role

He went to the town of Sarov, 400 kilometres (249 miles) east of Moscow, which is marking the 100th anniversary of the canonisation of St Seraphim with a vast pilgrimage.

The saint's birthplace is also home to a closely guarded nuclear weapons facility and the president praised its continuing work.

His attendance at the pilgrimage and his gift of a new bell to Sarov's cathedral, a BBC correspondent reports, indicate the importance Mr Putin places on religion in the modern state.

"I would like to thank the representatives of the Russian Orthodox Church for strengthening the moral foundations of the Russian state, and strengthening the agreement between the peoples of our nation," said Mr Putin on his visit.

The former KGB officer, an avowed Russian Orthodox believer, attended a service in the cathedral, emerging alongside Patriarch Alexi II.

It was, the BBC's Sarah Rainsford reports, a powerful image formed by two powerful men.

The Church's influence in post-atheist Russia is clearly growing, she says, along with its congregation and with elections looming later this year, the Orthodox president will be hoping he can count on the vote of the faithful.

Nuclear component

President Putin pledged support to scientists at the Federal Nuclear Centre in the town, known in Soviet times as Arzamas-16, which is still closed to outsiders.

The centre incorporates several dozen research institutions and has 18,000 workers on its payroll, the Russian news agency Itar-Tass reported.

Nuclear forces "have always been one of the main components of state security", Mr Putin told scientists.

"There is no doubt that since we have such people, they [nuclear forces] will remain so for a long time."

The president also promised that Russia would "continue to develop everything necessary to provide proper support for scientific and applied research".

Revered saint

St Seraphim is one of the most venerated saints of the Russian Orthodox Church, our correspondent says, and his Holy Day is one of one of the most important in its calendar.

Instead of condemning others, strive to reach inner peace. Keep silent, refrain from judgement St Seraphim quotation

Thousands of pilgrims have come to the area to pay tribute to a holy man who devoted his life to prayer and healing.

A final mass on Friday marks the culmination of four days of celebration which have already seen a procession of 10,000 priests and believers carrying his relics from Sarov to a convent in the village of Diveyevo.

Pilgrims have included the Anglican Archbishop of Canterbury.

Perhaps mindful of Russia's large Muslim minority, Mr Putin was careful to extol all of the country's recognised religious faiths.