A man and his nephew have been arrested over the murder of New Zealand tourist Nicholas Heyward in an Argentinian park.

Argentinian police have arrested a man and his nephew over the murder of New Zealand tourist Nicholas Heyward in a Mendoza park.

The Australian-based Kiwi, aged 31, was shot dead when two motorcycle-riding robbers, known as “motochorros”, tried to snatch his bag while he strolled through a park in the city of Mendoza in April.

Mr Heyward was shot up to four times between his chest and neck with a .22 pistol, police say.

He had been travelling after finishing a degree in physiotherapy at the University of Queensland and been in Central America for about a year.

He was planning to return in a few months to Australia, where he has family in Adelaide and on the Gold Coast.

Marco Leiva Soda, 34, and his nephew, Adrian Soda, 20, have been charged with Mr Heyward’s murder, Argentinian newspaper Los Andes reports.

The pair were arrested (local time) after four raids in La Favorita, a neighbourhood in the west of the city, where the motorbike believed to have been used in the murder was found.

Both have a long criminal history involving aggravated robbery and attempted murder.

The murder weapon still hasn’t been found, and police are continuing to analyse material recorded on security cameras in the area.

Argentina’s Ministry of Security offered 40,000 pesos (about $A5446) to help find the offenders.