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Argentine President Cristina Fernandez met with a frail-looking Fidel Castro on Sunday while in Cuba for a regional summit, posting pictures of the two smiling together on her Twitter account.

Castro, who is rarely seen in public ever since delegating power to his brother Raul in 2006, was wearing one of his customary tracksuits in the photos. In one shot, Castro appears to signing photos of himself for Fernandez.

Fernandez wrote on Twitter that Castro had invited her to lunch along with his daughter, Florencia. She said she was “enchanted” by the meeting and, offering a glimpse of the meal conversation, said the two leaders shared “infinite nostalgia” for the late Hugo Chavez.Fernandez is in Havana to attend the second Summit of the Community of Latin American and Caribbean States (CELAC). Castro is holding private meetings with some of the heads of state in town for the meeting in an unofficial capacity.

The two-day summit, perhaps ironically, coincides with the 50th anniversary of when many Latin American countries broke diplomatic and economic ties with Castro’s government.

NBC's Mary Murray contributed to this report from Havana.