Nejat Ceylan, 50, failed to notify authorities of his address and hasn't been seen since May 9.

"His current whereabouts is unknown and the address that he has previously stated is not where he is residing," Assistant Commissioner Neil Paterson told reporters on Thursday.

Ceylan, who is on the sex offenders registry for possessing child pornography, may be living in the Roxburgh Park area but is also known to frequent Broadmeadows, Richmond and Melbourne CBD.

Mr Paterson believes Ceylan is deliberately evading police, having already racked up multiple convictions for failing to comply with his reporting obligations.

"We think (he's) still in the local area but avoiding police. He has a history of evading police so this is usual behaviour for him," he said.

Ceylan is described as about 170cm tall, with a medium build, brown eyes, grey hair and a beard. He also goes by a number of aliases.

Mr Paterson said anyone who sees Ceylan should not approach him but call triple-zero.

"When registered sex offenders are non-compliant with their reporting obligations, when they are actively avoiding police, the risk of reoffending increases and therefore the risk of harm to the community increases," he said.

Ceylan does not wear an ankle bracelet and was not affected by the Telstra blackout earlier in the week, which made dangerous criminals and sex offenders untraceable for at least two hours.

Australian Associated Press