Arsenal consolidated fourth spot in the Premier League after drubbing Leeds United 4-1 at Elland Road on Saturday evening.
The Gunners were unchanged from their win over West Ham United, with Alexandre Lacazette leading the front-line in the continued absence of Pierre-Emerick Aubameyang, supported by Martin Odegaard, while injury-hit Leeds' bench comprised mostly of teenagers.
The Whites' goalkeeper IIlan Meslier was already exposed in the opening exchanges, having to make crucial saves but he was eventually beaten in the 16th minute after Martinelli fired a loose ball in the box into the top corner.
Mikel Arteta's charges remained on the front foot and Martinelli doubled their lead and grabbed his brace just before the half-hour mark with a chip Meslier and into the back of the net after going through on goal from Granit Xhaka's pass.
Marcelo Bielsa's men had their backs against the wall and Bukayo Saka made it 3-0 for Arsenal just before the half-time break with a deflected strike in the box that wrong-footed Meslier.
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The game was getting physical early in the second stanza, with the Gunners restricted from having clear chances and Arteta was forced to make a change in the 64th minute as Takehiro Tomiyasu got injured and he was replaced by Cedric Soares at right-back.
Leeds had a lifeline in the 73rd minute after they were awarded a penalty for a sliding challenge by Ben White on Joe Gelhardt and Raphinha fired the spot-kick away from goalkeeper Aaron Ramsdale and into the top corner, 1-3.
However, substitute Emile Smith Rowe put the game to bed for Arsenal six minutes before time with a strike past Meslier after a through ball by Odegaard and the Gunners went four points clear of fifth-placed West Ham in fourth spot on the log.