Abbas dismissed Brigadier General Abd al-Razaq Majaidi, the chief of public security, national police chief Saib al-Ajiz and the commander of the security forces in the southern Gaza, Umar Ashur, on Thursday.
The sacking comes just hours after Abbas ordered security forces to stop fighters from firing mortars and rockets at illegal Jewish settlements in occupied Gaza.
Hamas fighters fired more than 30 mortars and rockets at various colonies on Thursday, causing no casualties or damage.
According to an Hamas spokesman, the attack was carried out in retaliation to the killing of two Palestinians at the hands of Israeli occupation forces a day after the Sharm al-Shaikh summit.
Abbas has said he is committed to reforming the Palestinian security forces. Last month he ordered that more than 1000 veteran officers be retired.
On Tuesday, at the Sharm al-Shaikh summit, the president and Israeli Prime Minister Ariel Sharon declared an end to violence against Palestinians and Israelis.