Police in the French city of Lyon have released an initial suspect in the Saturday shooting of a Greek Orthodox priest after finding no evidence of his involvement.

The priest was shot with a hunting rifle while he was closing the church, and was left seriously wounded.

Following the incident, officials have opened an investigation for attempted murder. Reports have suggested a possible personal motive.

The shooting came only two days after three people were killed in a knife attack at a church in Nice. An investigation into that incident is ongoing.

France raised its national terror alert guidance Thursday to its highest "emergency" level, with up to 4,000 military personnel to be deployed to boost security at schools, churches and other places of worship.