Agencies/London

The prime suspect in the disappearance of schoolgirl Alice Gross was a “callous and heartless murderer”, the mother of the wife he battered to death said.

Convicted killer Arnis Zalkalns, 41, was named as wanted for questioning by Scotland Yard after he was identified cycling along the same towpath as Alice on the day she went missing three weeks ago, 15 minutes after she walked the route.

Police in Europe said the Latvian builder had been jailed in 1998 for the murder of his wife Rudite Zalkalns, 22, in his homeland. He served seven years of a 12-year sentence. Zalkalns went missing a week after 14-year-old Alice was last seen on August 28, when she was spotted on CCTV by the Grand Union Canal near her home in Hanwell.

His wife’s mother Viktorija Zalkalns, 70, condemned the seven-year sentence he served as disgracefully short. She told how Zalkalns, who took his wife’s name when they married, tricked Rudite into going into a forest, where he bludgeoned her over the head with a scaffold pole before stabbing her. He then pushed her body into a grave he had dug.

Zalkalns told the Daily Mail: “I always feared he might kill again. Once you have tasted blood the taste stays and you never stop. He killed our lovely daughter and destroyed our family. This was a callous and heartless murder.”

Detectives also revealed that Zalkalns, who works as a building labourer at a site in Isleworth, was arrested on suspicion of indecent assault on a 14-year-old girl in Ealing in 2009, but the case was dropped when the victim refused to give further evidence. Scotland Yard said there was no record in the UK of Zalkalns’s murder conviction when he arrived in 2007.

Zalkalns disappeared on the night of September 3 from the Ealing home he shared with his partner and one-year-old daughter.

He is described as white, 5ft 10in, of stocky build, with dark brown hair that he normally wears in a pony tail.

A reward of up to £20,000 is being offered for anyone who has information that leads detectives to find Alice.

Meanwhile detectives are hoping for a breakthrough after finding the bike belonging to Zalkalns.

Zalkalns’s red Trek mountain bike will be subject to forensic tests which police hope will help them piece together what happened.

Scotland Yard would not say where the bike was found or what condition it was in. An alert has been issued to all ports and airports for Zalkalns to be prevented from leaving the UK. Police say that family and colleagues have told them Zalkalns was behaving normally in the days before and after Alice’s disappearance.

His family home in west London has been searched and items removed for further examination.