A teen volunteer with the Rural Fire Service in NSW has been charged after allegedly lighting seven fires in the Bega Valley area.

Blake William Banner, 19, allegedly lit a fire on Tuesday afternoon next to the Bega river, left the area and returned to fight the fire for the RFS.

AAP

He was arrested at a Tarraganda fire shed within two hours of the fire.

Banner was charged with causing the fire as well as six others since 17 October, and appeared before Bega Local Court on Wednesday. He was granted conditional bail to return to the court on 17 December.

As part of his bail agreement, Banner is not permitted to possess any firefighting equipment or implements.

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The RFS said it had immediately stood down the 19-year-old and had a "zero tolerance" approach to arson.

"Our members will be rightly angry that the alleged actions of one individual can tarnish the reputation and hard work of so many," RFS Commissioner Shane Fitzsimmons said in a statement on Wednesday.

This type of alleged behaviour is the ultimate betrayal RFS Commissioner Shane Fitzsimmons

"This type of alleged behaviour is the ultimate betrayal of our own members, and of the broader community."

In a separate incident, a 33-year-old man has also been charged over a fire-lighting spree which destroyed four cars in the NSW Hunter.

Police arrested the man on Tuesday after the string of fires were allegedly lit in Lake Macquarie suburbs between 8 November and 19 November.

Four cars were destroyed on a single night, police said.

At 8.30am there are 129 fires burning, 66 are uncontained. One fire is at Watch and Act level. More than 1,800 personnel are working to contain these fires. Severe and High Fire Danger Ratings continue over much of the state today. #nswfires #nswrfs https://t.co/oTrzcu7HDR pic.twitter.com/L1IiXiUBqb — NSW RFS (@NSWRFS) November 26, 2019

"Acts of arson at any time of year are extremely dangerous, let alone during the high temperatures we have recently experienced," Superintendent Danny Sullivan said in a statement on Wednesday.

The man has been charged with 12 counts of destroying property with fire and has been refused bail to facet Belmont Local Court on Wednesday.

Almost 130 bush and grass fires are burning around NSW.