Magomed Yevloyev, who ran a Web site on government corruption and police abuse, was shot in the head Sunday in a police car taking him to a station for questioning, the Washington Post reported.
Colleagues of Yevloyev dismissed government contentions that he was shot while struggling for a gun held by an officer, the Post reported.
A posting on Yevloyev's Web site, Ingushetiya.ru, called for a mass protest Monday in Nazran, Ingushetia's main city and the scene earlier this year of violent clashes between anti-government protesters and security forces.
Yevloyev was seized Sunday when he arrived in Ingushetia after spending several months in Moscow.
A passenger on the plane with him told the Post Ingushetia regional President Murat Zyazikov was on the same flight and called police to the airport after recognizing Yevloyev.