During his visit Castro and Russian President Dmitry Medvedev signed a memorandum on "strategic" cooperation and reached an agreement to grant the Caribbean state a $20 million loan tentatively to buy Russian-made construction, electricity-generating and agricultural equipment.
Russia also promised substantial food aid to alleviate an acute food problem on the island badly affected by two tropical hurricanes, Gustav and Ike, in September 2008.
Russia's foreign trade bank Vnesheconombank (VEB) said it had opened credit lines totaling $44.5 million to fund the purchases of Tu-204CE civilian cargo aircraft and equipment by Cuba.
Over 30 documents were signed as part of Castro's Russian visit, including memos on cooperation in trade, education, sport and tourism.
Opening the talks on Friday, Medvedev said the two countries should increase their trade turnover, which currently stands at a "meager" $239 million.
He said Castro's visit would "open up a new page in the history of Russian-Cuban relations." And the Cuban leader called their talks "historic" and a "milestone event" in bilateral ties.
Relations between Russia and Cuba stalled after the collapse of the Soviet Union, when Russia faced by financial difficulties halted huge Soviet-era subsidies and trade.
In recent years, Russia has moved to revive ties with Cuba, as well as other Latin American states. Medvedev visited Havana in November, and a Russian anti-submarine destroyer and two logistical warships docked in Cuba in December.
Last Thursday, the two leaders enjoyed a nostalgia-tinted informal meeting at the presidential Soviet-era country residence at Zavidovo.