An eight-year-old boy had his foot partially severed when he was knocked over and dragged beneath a ride-on lawn mower in a park in south Oxfordshire.
Damon King, of Reading, Berkshire, was playing tag with a friend near Henley-on-Thames when they were both knocked down by a reversing grass cutter.
His friend was knocked down first but escaped serious injury, Damon's mother Carolyn King said.
Damon's foot was "practically severed" when he was dragged under it, she said.
I thought the worst had happened because I saw the mower roll over him and roll off him
The keen track and circuit cyclist was visiting Binfield Heath recreation ground last Tuesday for a family picnic.
The boys had been running around and were coming back to rejoin the family to get some water when they collided with the reversing lawn mower, Mrs King said.
She added: "He was so silent and still at first, I thought the worst had happened because I saw the mower roll over him and roll off him.
"I ran over and tried to pull him out and was actually quite relieved when it was just his foot.
"He was screaming and kept looking down at it and trying to get away from it."
Damon was airlifted to Wexham Park Hospital and underwent two four-hour long operations.
He is expected to need up to three more operations to rebuild it, Mrs King said.
Binfield Heath Parish Council said it took its safety responsibility for the playground seriously and carried out frequent recreation ground safety inspections.
A council spokesman said a local firm had been engaged for many years in Binfield Heath and neighbouring parish councils to cut the grass and it had never had any complaints about either the contractor or the park's safety standards in general.
It said councillors believed the appropriate safety policies had been followed and Thames Valley Police were investigating.