The Palestinian National Authority (PNA) extended on Monday its support to the Egyptian leadership and people after Sunday's deadly attack against a security checkpoint in North Sinai.

Nabil Abu Rdineh, a spokesman for the PNA, said that the attack, which had left at least 16 Egyptian soldiers killed and seven others injured, is "a heinous crime and an act of terrorism."

The gunmen remained unidentified although Egyptian sources suspect that they came from the neighboring Gaza Strip. They later seized an armored vehicle and headed for the Israeli border.

Israeli sources said that the attackers failed to penetrate into Israel and were killed immediately.

Abu Rdineh denied any Gaza or Hamas connection with the attackers, saying that the security of Egypt and its people are intertwined with the Palestinian security and wellbeing.

He added that the PNA respects the sovereignty of Egypt, noting that the strong relation between the Egyptian and Palestinian leadership has not been undermined.

Gaza is connected with Sinai via a network of underground tunnels that Hamas has licensed after it wrested control of the territory in 2007.

The sole Palestinian border to the outside not shared with or controlled by Israel is the Gaza-Egypt Rafah crossing, which was closed by Egypt after the attack.