MOSCOW (Reuters) - Valentina Matvienko, the speaker of the upper house of the Russian parliament, said on Tuesday that the resignation of Nursultan Nazarbayev, the president of Kazakhstan, was unexpected and very serious, the RIA news agency reported.

Matvienko is a close ally of President Vladimir Putin.

Nursultan Nazarbayev said on Tuesday that he was resigning as the oil-rich Central Asian nation’s leader after three decades in power.