So you agree with Mike that it is a coralline Limestone.
Andrey,
You confirmed that this specimen is colonial coral, in this case, if you agree with me, according to the arrangement of Septae (the first images), we can guess a scleractinian corals.
most likely it is a rugose coral of Devonian age. It is hard to say which genus it belongs to, but I would suggest it is a Phillipsastrea. Thin sections or polished surfaces would help... I would not be so sure about a Scleractinian coral...
I agree with you all, this specimen looks like a rugosa coral, I don't think it before!.
Until preparing a thin section, we can suggest that this specimen is a colonial rugose coral of Devonian age. Which the genus is probably belongs to a Phillipsastrea (according to Stefan).
Syed, thank you for the attached file it was very interesting.
Thank you so much for your answer, So you confirm that this specimen is a rugose coral of Devonian age. As Stefan suggest that the genus could be a Phillipsastrea.
I agree with Stefan, but only thin sections will confirm (beautiful specimen). It certainly looks Devonian and mostly likely Phillipsastrea or Hexagonaria. It is difficult to see from the photographs, but it looks like the corallite walls are better developed than you might expect in Phillipsastrea, hence it could be more like Hexagonia.