O’Connor, 20, and Yarney, 19, have both put pen to paper on contracts at St. James’ Park, and will link up with Peter Beardsley and Ben Dawson’s Under-23s squad.

London-born centre half O’Connor joins the Magpies after leaving Arsenal in the summer, where he had spent seven years since signing from Crystal Palace.

Having been capped by England at England Under-17 level, he made one senior appearance for the Gunners, coming on as a substitute in a Champions League win against Galatasaray in December 2014.

O’Connor has also spent time on loan at then-League Two side York City and Dutch outfit MVV Maastricht.

Yarney, meanwhile, is also a defender, and arrives on Tyneside after leaving Everton earlier in the summer.

While at Goodison Park, the Liverpool-born youngster progressed through the ranks to second-string level, making three appearances for the Toffees’ Under-23s side in the Checkatrade Trophy last term.

He featured once as a trialist for the Magpies’ Under-23s last season, coming on as a substitute during their final Premier League 2 game of the season, a 2-0 victory at Middlesbrough in April.

Both players have begun pre-season training with the rest of United’s development squad at the Little Benton Academy, and could feature when the Under-23s travel to Darlington for their first pre-season friendly on Monday, 17th July.

Meanwhile, United have received international clearance for fellow youngsters Juanito and Tyrique Bartlett.