The likely suspect in a deadly blast in the Russian city of St. Petersburg is a Kyrgyz-born Russian citizen, Kyrgyzstan's security service said on Tuesday.

A spokesman for the GKNB security service said it had received an official request from Russian security services to identify the suspect.

The spokesman declined to name the suspect or provide any additional information.

Kyrgyzstan, a predominantly Muslim Central Asian nation of six million, is Russia's close political ally and hosts a Russian military airbase.