(Adds context, background)
ALMATY, Oct 11 (Reuters) - Kazakh President Nursultan Nazarbayev is being treated for a cold, his office said on Tuesday, prompting speculation that the illness was diplomatic.
The announcement was unusual because the presidential office rarely provides any comments on the state of the 76-year-old leader's health, which is a state secret under Kazakh law.
But some, including Kazakh political analyst Aidos Sarym, say it was most likely an excuse to avoid visiting Armenia where the office of President Serzh Sarksyan had said earlier on Tuesday it expected Nazarbayev to visit on Oct. 13.
Armenia will host a top-level meeting of the Collective Security Treaty Organisation (CSTO), a Russia-led security bloc, on Oct. 14.
But Astana's ties with Yerevan have been strained since April, when during the renewed military conflict between Armenia and Azerbaijan, Kazakhstan insisted on holding a meeting of another regional body, the Eurasian Economic Union, outside of Armenia which was due to host it.
Both Kazakhstan and Azerbaijan are Turkic-speaking, predominantly Muslim nations. Azerbaijan also tranships a significant share of Kazakh oil exports.
Still, Nazarbayev's genuine health is a matter of concern for many, including energy majors who have invested billions of dollars in the country.
Since the death of Uzbek President Islam Karimov last month at the age of 78, Nazarbayev holds the distinction of being the only former Communist leader who still runs his nation after it gained independence in the break-up of the Soviet Union in 1991. (Reporting by Olzhas Auyezov; Editing by Andrew Osborn and Angus MacSwan)