Egypt has warned of a military response if Hamas or other Palestinian groups try to violate Egyptian security, increasing tension over what Cairo says is support from Gaza for Islamist militants operating in the Sinai Peninsula.
Egypt's army says militants from Hamas-run Gaza have staged joint attacks with hardline Islamists in North Sinai, where the government has ramped up security operations after a surge of violence set off by President Mohamed Morsi's downfall in July.
Foreign Minister Nabil Fahmy told the London-based newspaper al-Hayat there was "tension" in Cairo's relationship with Hamas, an ideological offshoot of Morsi's Muslim Brotherhood. He suggested Hamas was not helping enough to secure the border.
The Sinai militants expanded into a security vacuum that emerged after president Hosni Mubarak was ousted by a popular uprising in 2011.
"If Hamas proves through actions and not words - and unfortunately there are many negative indicators - its good intentions, then it will find an Egyptian party that ... protects the Palestinian side," Fahmy said.
"If we feel that there are parties in Hamas or other parties trying to violate Egyptian national security, our response will be severe," said Fahmy, foreign minister in the interim cabinet that came to office after Morsi was deposed by the army.
Asked whether any response would include a closure of the Rafah border crossing between Gaza and Egypt, Fahmy said: "Options are military-security, and not options that result in suffering for the Palestinian citizen."
The Rafah crossing is the only way in and out of Gaza not controlled by Israel, with which Egypt made peace in 1979.
Fahmy did not elaborate on what kind of military action Cairo might take.
Hamas has denied Egypt's accusations. A spokesman for the Hamas government said Fahmy's comments "contradicted Egypt's history and role in protecting the Palestinian nation".
Fahmy said: "There are very many flaws in the Hamas relationship with the former (Morsi) regime, and the relationship of Hamas, or other Palestinian Islamist parties, with terror activity in Sinai."
Morsi, deposed on July 3 after mass protests against his rule, is being investigated on accusations of conspiring with Hamas when he escaped from prison during the uprising against Mubarak.
Egypt's army spokesman said at a Sept. 15 briefing the military was clearing buildings deemed a security threat at a distance of up to one km (0.6 miles) from the Gaza border.
The spokesman declined to accuse Hamas directly of attacks, although he said hand grenades stamped with the name of the Palestinian group's armed wing, the Qassam Brigades, had been found in the security sweep under way in Sinai.