NSW bush search continues for 77-year-old

Police and volunteers are searching for a missing 77-year-old man - feared dead a month after he disappeared from a retirement home - in bushland on the NSW south coast.

Raymond Speechley, 77, who is understood to suffer from Alzheimer's, was last seen at the home in Dalmeny, north of Narooma, on July 7.

Police say they hold grave concerns for his safety.

A man matching the description of Mr Speechley - wearing jeans, a dark jacket and a pyjama top - was seen in the town days after he went missing.

About 50 volunteers were helping more than 40 police doorknocking and searching bushland in the area, an SES spokesman said on Saturday.

Authorities earlier said Mr Speechley could have been trying to travel to the Wollongong area and may have been assisted by a driver on the Princes Highway.

But they haven't found further evidence of that.