Three men convicted of gang-raping a teenage girl in Kenya and dumping her in a pit latrine have each received 15-year jail terms.

Reports that the rapists were ordered by police to cut grass as a punishment caused global outrage last year. The Kenyan police deny the claims.

Nearly two million people signed a petition demanding justice for the girl, known as "Liz".

Her mother told the BBC she was happy that justice had finally been served.

The girl was on her way home from her grandfather's funeral in western Kenya's Busia County in June 2013 when the assault took place. She suffered a broken back and serious internal injuries.

In October 2013, hundreds of people walked to the Kenyan police headquarters in Nairobi to deliver the petition. The case was subsequently referred to the country's judicial watchdog.

There are still arrest warrants outstanding for three other suspects in the case, who police say are on the run.

The hashtag #JusticeForLiz was trending on Twitter for several hours on Monday as news of the jail sentences spread.

Campaigners have welcomed the sentences, but have warned that fear and stigma still discourage many women from reporting sexual assault.

"An estimated 19 out of 20 rapes in Kenya are not reported and are therefore unpunished," said Kimberly Brown, from campaign group Equality Now, quoted in local media.