LANKARAN, Azerbaijan -- Police in the southeatern Azerbaijani city of Lankaran have jailed an activist for "disobeying the police," a charge his relatives are calling politically motivated.

Elvin Irsadov, known on Facebook as Umar Ali, was detained on May 18 and sentenced the next day to 16 days in jail, his sister, Aynur Irsadova, told RFE/RL.

According to Irsadova, the 30-year-old Elvin's incarceration was retaliation by the police for his online activities.

She said her brother was threatened by a district policeman in Lankaran for sharing images on Facebook that purportedly show police brutality. The policeman also demanded Irsadov delete the pictures.

The day before his arrest, Irsadov wrote on Facebook that an unknown individual had threatened and insulted him, and later spread false information about him.

In one recent post, Irsadov criticized the government's anti-corruption efforts, saying that the widely announced arrests of officials in the country were in fact just for show and not part of a real fight against corruption.

Critics of Azerbaijani President Ilham Aliyev say the authorities in the energy-rich South Caucasus state frequently jail opposition activists, reporters, human rights defenders, and civil society advocates without grounds in an effort to silence dissent.

Aliyev, who has ruled Azerbaijan since shortly before his father's death in 2003, has rejected the criticism.