* Plane shot down in July 2014, killing all 298 aboard
* Russia's 53rd Anti-Aircraft Brigade named in shooting
* Russia denies involvement, dismisses findings as baseless
* Prosecutors have narrowed suspect list to "dozens", seek tips
* Dutch leader cuts short India trip to discuss MH17 (Adds U.S. State Department comment, paragraphs 8-9)
By Anthony Deutsch
BUNNIK, Netherlands, May 24 (Reuters) - Dutch prosecutors identified a Russian military unit on Thursday as the source of the missile that shot down Malaysia Airlines Flight 17 over eastern Ukraine in 2014, killing all 298 people on board.
The airliner flying from Amsterdam to Kuala Lumpur was hit by a Russian-made "Buk" anti-aircraft missile on July 17, 2014 over territory held by pro-Russian separatists. There were no survivors. Two thirds of those killed were Dutch.
"The Buk that was used came from the Russian army, the 53rd brigade," Chief Dutch Prosecutor Fred Westerbeke told Reuters. "We know that was used, but the people in charge of this Buk, we don't know."
Russia repeated on Thursday that it had nothing to do with the incident.
"Not a single air defence missile launcher of the Russian Armed Forces has ever crossed the Russian-Ukrainian border," Russia's TASS news agency quoted the Defence Ministry as saying in a statement.
Russia's Foreign Ministry said the findings had been based on fake data presented by bloggers and that Moscow's information regarding the case had been largely ignored.
"This is an example of baseless accusations aimed at discrediting our country in the eyes of the international community," the Russian Foreign Ministry said in a statement.
The U.S. State Department said on Thursday the United States had "complete confidence" in the findings and called on Russia to admit its involvement.
"It is time for Russia to cease its lies and account for its role in the shoot down," spokeswoman Heather Nauert said in a statement.
Investigators appealed to the public to come forward and help identify members of the crew who operated the missile and determine how high up the chain of command the order originated.
"The Russian Federation didn't help us in providing us the information we brought out into the open today," Westerbeke said. "They didn't give us this information, although a Buk from their military forces was used."
Prosecutors showed photos and videos of a truck convoy carrying the system as it crossed the border from Russia to Ukraine. It crossed back several days later with one missile missing. The vehicles had serial numbers and other markings that were unique to the 53rd Brigade, an anti-aircraft unit based in the western Russian city of Kursk, they said.
In the interim update on their investigation, prosecutors said they had trimmed their list of possible suspects from more than a hundred to several dozen.
Westerbeke said investigators were not yet ready to identify individual suspects publicly or to issue indictments, but that when they do he expects cooperation, or a firm international political response.
HOLD RUSSIA ACCOUNTABLE
Dutch Prime Minister Mark Rutte cut short a trip to India to return in time for a cabinet meeting on Friday to discuss the latest findings in the inquiry.
The MH17 Disaster Foundation representing families of the victims demanded that the Dutch government take legal action to hold the Russian state accountable.
"It must go beyond legal exploration after this," board member Piet Ploeg was quoted by broadcaster NOS as saying.
A Joint Investigation Team, drawn from Australia, Belgium, Malaysia, the Netherlands and Ukraine, is gathering evidence for a criminal prosecution in the downing of the plane.
Ukrainian Army General Vasyl Hrytsak, a member of the investigation team, told Reuters the next crucial step would be to pinpoint who issued the orders to move the missile system.
The Dutch Safety Board concluded in an October 2015 report that the Boeing (NYSE:BA) 777 was struck by a Russian-made Buk missile.