MOSCOW, April 16 (Reuters) - Russia summoned Mexico's ambassador on Thursday ‌to express strong concern over ‌what it cast as inaction by Mexican ​authorities in a case involving an underage Russian citizen in the custody of Mexican social services.

Foreign Ministry ‌spokeswoman Maria ⁠Zakharova said that the Russian girl, Kristina Romanova, had ⁠been taken into custody illegally by Mexican authorities.

Mexican ambassador Eduardo Villegas ​Megías was ​told that ​Russia demanded immediate ‌consular access to the girl.

"Against the background of ignoring repeated appeals from Moscow, the Russian side strongly demanded immediate consular access to the ‌Russian minor and ​the establishment of ​all necessary ​conditions for her unhindered ‌return to her homeland," ​the foreign ​ministry said.

The Mexican embassy could not be reached for immediate ​comment.

(Reporting by ‌Dmitry Antonov, Writing by Guy ​Faulconbridge and Anna Peverieri; editing ​by Andrew Osborn )