Approximately 150 people broke through the IDF checkpoint at the Homesh outpost in the West Bank on Wednesday evening and entered the settlement, according to Army Radio.
Israeli security forces are reportedly preparing to evacuate them.
This comes shortly after the Knesset repealed the 2005 Disengagement Law on Monday night.
What is the significance of the Disengagement Law's repeal?
The legislation removes the ban on the entry of Israelis to the site of the four destroyed settlements – Homesh, Sa-Nur, Ganim and Kadim — which are now closed military zones. Passage of the bill does not impact the 2005 withdrawal from Gaza, which remains in force. It is limited solely to northern Samaria.
The repeal of the Disengagement Law only lifts the ban on Israeli citizens entering the area and does not automatically approve the reestablishment of the four evacuated settlements.
The status of the land will now be like the rest of Area C, meaning that any further restrictions or permits concerning entry and building in the area will be up to the IDF and the government.
This is a developing story. Tovah Lazaroff and Tzvi Joffre contributed to this report.