The man was "suspected of complicity in the perpetrator's actions on February 14 and 15," police said in a statement.
"Like yesterday, a number of raids are being carried out in connection with the arrest," it added.
A fourth man was arrested yesterday in a downmarket area of Copenhagen, bordering the Noerrebro neighbourhood where El-Hussein lived.
Custody hearings held today for the men, who cannot be named for legal reasons, were not open to the public.
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They were also charged with helping him get rid of clothing after the attack and for providing "other equipment" for the shooting that took place a few hours later outside a synagogue, where a Jewish man was killed.
The charges, which both men deny, did not specify what type of equipment they had given him before the second attack.
The 30-year-old reportedly wore a red hoodie when entering the court and threw a kiss at his girlfriend, who cried when the charges were read. The 25-year old wore a black hoodie.
Two other alleged accomplices have been detained since February 16 and a third since February 27, on suspicion of helping the 22-year-old gunman obtain and dispose off weapons.