Avril Lavigne and Chad Kroeger working on new music

Estranged couple Avril Lavigne and Chad Kroeger have reunited for songwriting sessions just a month after they announced their divorce.

The Sk8er Boi singer revealed her separation from the Nickelback rocker in September (15) following two years of marriage.

The former couple began their romance when Chad helped Avril write songs for her fifth album in 2012, and they are continuing to create songs together for her next disc, despite the breakdown of their marriage.

Avril shared a picture of herself in a straw hat holding an acoustic guitar on Instagram.com and wrote in the caption, "YeeHaw! Writing with Chad today," before sharing a snap of Chad smiling and holding another guitar, with the caption, "Back where it all started..."

The Canadian pop star announced the split on the social media site with a photograph from their wedding day.

She told fans, "It is with a heavy heart that Chad and I announce our separation today... Through not only the marriage, but the music as well, we've created many unforgettable moments. We are still and forever will be, the best of friends, and will always care deeply for each other. To all our family, friends and fans, thank you sincerely for the support."

Avril was previously married to Sum 41 rocker Deryck Whibley.