A 13-year-old boy who used a water bottle to attack a man before stealing his car and immediately crashing it because he did not know how to drive, has been jailed for a year.

A three-month-old female infant was in hospital with serious injuries after a man allegedly attacked her and the woman carrying her, in an alleged assault in an unspecified area in the Victoria Daly region on Tuesday afternoon, NT Police said.

An 11-year-old boy and a 14-year-old – the second who allegedly spat in the face of an officer – were arrested after they were allegedly caught on a vandalism spree that included violence, as well as car damage and rock throwing at the polling booth in Casuarina Library Tuesday afternoon, NT Police said.

A motorbike rider was clocked riding at 202km/h in a 100km/h zone in Hidden Valley on Sunday night, NT Police have said, with the alleged offence following the death of two men men on the Barkly Hwy after their car hit a tree on Saturday afternoon.

A South African mechanic who used a belt and his fists to violently beat his three step children who were aged under 11, has been released after four months in jail.