Germany loaned Lithuania its long-lost declaration of independence on Wednesday as the Baltic nation prepares to mark one hundred years since it restored statehood after World War I.

The 1918 document, which was unearthed in a Berlin archive last year by a Lithuanian professor, will stay in the country for five years under a bilateral agreement.

"I want to thank our friend Germany which managed to preserve the document of great importance for us during turbulent times," Lithuania's President Dalia Grybauskaite said as she received the document during a ceremony in capital Vilnius.

"After a 100 years the Act of #Lithuania's Independence is finally back home!," she added in a tweet.

The arrival of the document, which has been called the country's "birth certificate", launches year-long festivities including an Independence Day celebration on February 16 when EU leaders will travel to Vilnius to mark the 100th anniversary of the declaration.

Lithuania's Catholic Church has also given its faithful a special gift by allowing them to eat meat on the national holiday, which falls on a Friday during Lent when Christians must observe a period of fasting.

Lithuania ruled over one of medieval Europe's largest military empires, encompassing large territories of present-day Belarus, Ukraine, Poland and Russia, stretching from the Baltic to the Black Sea.

But by the late 1700s, the Kingdom of Poland and the Grand Duchy of Lithuania were gradually partitioned between neighbouring empires.

Russia ruled Lithuanian territories until the empire's collapse during World War I.

Historians say that up to five copies of independence declarations could have been signed on February 16, 1918, when Lithuania was under German occupation, but all traces of other copies vanished.

During World War II, the Soviet Union occupied and annexed Lithuania, which became the first Soviet republic to declare independence in 1990.

The nation of 2.8 million joined EU and NATO in 2004. Lithuania has repeatedly warned its Western allies of Russia's imperial ambitions, notably after Moscow annexed Ukraine's Crimea peninsula in 2014.