* Putin says developing navy a priority
* New submarine designed to launch ICBMs
* Russia planning Mediterranean naval exercises
By Steve Gutterman
MOSCOW, Jan 10 (Reuters) - Russia inaugurated on Thursday the first of a new class of submarine it will rely upon for decades as a bulwark of its strategic nuclear force and President Vladimir Putin pledged to strengthen the country's navy further.
Putin, who began a new six-year term last May, has emphasised that Russia sees nuclear arms as a crucial source of security and will continue to rebuild its sea power after a period of shrinkage following the 1991 Soviet collapse.
Defence Minister Sergei Shoigu reported to Putin that the first of the Borei class nuclear-powered submarines, the Yuri Dolgoruky - on which construction began in 1996 - had entered service.
Shoigu spoke to Putin via a videolink from aboard the 170-meter (558-foot) submarine designed to carry 16 Intercontinental Ballistic Missiles (ICBMs) of a new type called the Bulava.
"Comrade commander-in-chief! ... The vessel has been handed over to the Russian navy," Shoigu told Putin in a message shown on state television from the Sevmash shipyard in the White Sea port of Severodvinsk.
The Russian president was on a visit to the Barents Sea naval base of Severomorsk at the time.
"The development of a powerful, effective navy is one of Russia's chief priorities," Putin said.
"We will only increase the pace, the renewal and development of the fleet," he said in televised comments at the base, where he gave an award to the crew of the Northern Fleet's flagship, the warship Pyotr Veliky.
Putin said the state has earmarked more than 4 trillion roubles ($132 billion) by 2020 to upgrade naval forces.
He reiterated plans to bring eight Borei submarines designed to launch ICBMs into service in that period, in addition to eight smaller Yasen type submarines, also atomic-powered.
Russian navy chief Admiral Viktor Chirkov said the Yuri Dolgoruky was expected to go on combat duty early in 2014 after a series of exercises, state-run news agency RIA reported.
Russia and the United States signed a landmark treaty in 2010 setting lower limits on the size of the long-range nuclear arsenals they built up during the Cold War.
But the limited numbers of warheads and delivery vehicles such as submarines that they committed to under the New START treaty are still enough to devastate the world, and Putin has made clear Russia will continue to upgrade its arsenal.
Moscow has warned it could withdraw from the treaty if it believes that an anti-missile shield the United States is building in Europe, which Moscow says may be able to intercept Russian missiles within several years, has become a serious threat.
Several tests of the Bulava, which began in 2004, were failures, but Dmitry Medvedev, then President, said the missile was ready for use after two successful test launches from the Yuri Dolgoruky in late 2011.
"The navy has absolutely no grounds to doubt the reliability of this ... new sea-launched missile," Putin's chief of staff Sergei Ivanov, a former defence minister, said on Thursday, state news agencies reported.
Putin also presided at the inauguration on Thursday of a new icebreaker to service oil platforms, part of a series of events that seemed choreographed to display Russia's aspirations as a sea power.
Shoigu reiterated plans, announced by the Defence Ministry last week, for naval exercises in the Mediterranean Sea that he said would be "the biggest in the history of the country".
Russian officials have given no indication that the exercise planned later this month is linked to the situation in Syria, where Russia maintains a modest supply facility that is its only military base outside the former Soviet Union.
Russia has shielded President Bashar al-Assad by vetoing U.N. Security Council resolutions aimed to pressure or push him from power during nearly 22 months of violence, but says it will evacuate its citizens from Syria if necessary.