Four-time champion Serena Williams made a winning return at the Internazionali BNL d'Italia on Monday.

The 37-year-old beat Sweden's Rebecca Peterson 6-4, 6-2 to reach the second round where she will play sister Venus.

Forced out of the Miami Open due to a knee injury, the 23-time Grand Slam champion was playing her first match since March.

"It felt good to be back in the match," Williams told a post-match press conference.

"It's been a while. I haven't played a ton of matches this year. Not my choice, just by force. I really, really desperately wanted to be on the tour and to be playing, but it hasn't been able to work out.

"It felt good to finally be back out. Hopefully I'll be able to keep it up."

Venus beat Belgium's Elise Mertens 7-5, 3-6, 7-6(4) later in the day.

Meanwhile, Britain's Johanna Konta beat Alison Riske 6-4, 6-1. Konta won 40 per cent of her break points to help her progress to the last 32 where she will play seventh seed Sloane Stephens.

The USA's Madison Keys beat Polona Hercog 6-4, 7-6(3) and 2017 Wimbledon champion Garbine Muguruza triumphed over Saisai Zheng 6-4, 6-1.

Former French and US Open champion Victoria Azarenka beat China's Shuai Zhang 6-2, 6-1.