Germany on Friday called for the release of ousted Egyptian president Mohammed Morsi amid mounting tensions between supporters and opponents over his overthrow.

"We call for an end to the restrictions on Mr Morsi's whereabouts," a foreign ministry spokesman told reporters.

Tens of thousands of supporters of ousted president Mohammed Morsi gathered Friday vowing to keep fighting for his reinstatement, as rival rallies defending his overthrow underlined Egypt's bitter divisions.

The rallies come as Germany called for the release of Morsi, who is being held in a "safe place, for his safety" and has not yet been charged, according to the foreign ministry.

Jordan breathed a sigh of relief when Egypt's Muslim Brotherhood president was ousted because of the influence of its own opposition Islamists who have pressed for reforms, analysts say.

King Abdullah II and the government were quick to congratulate Egypt's Supreme Constitutional Court Adly Mansour hours after he was declared caretaker president by army chief Abdel Fattah al-Sisi following Mohammed Morsi's ouster on July 3, stressing support for "the will and choice of the great Egyptian people".

Militants killed an Egyptian police officer on Friday when they attacked a checkpoint in Sinai with rocket-propelled grenades, security and medical officials said.

The attack, which targeted a police armored vehicle at a checkpoint, also wounded a police conscript, the officials said. The officer killed was a lieutenant colonel, they added.

U.N. leader Ban Ki-moon on Thursday raised concerns about the detention of ousted Egyptian president Mohammed Morsi and other Muslim Brotherhood leaders with the country's foreign minister, a spokesman said.

Ban reaffirmed that there must be no "retribution" against any party after the military coup against Morsi, U.N. spokesman Martin Nesirky told reporters after the telephone talks between the U.N. secretary general and Foreign Minister Mohammed Kamal Amr.

The people of Egypt are marking the Muslim fasting month of Ramadan amid soaring tensions following last week's ouster by the military of Islamist president Mohammed Morsi.

"This year there is not the usual feeling of happiness. We are worried," said Fawziya, as she shopped in a Cairo market.

The United States is pressing ahead with plans to deliver four F-16 fighters to Egypt despite a military coup against President Mohammed Morsi, a U.S. official said Thursday.

"It's still the status quo," the official, who spoke on condition of anonymity, told Agence France Presse.

A Coptic Christian man was found decapitated on Thursday in Egypt's Sinai peninsula five days after he was kidnapped by gunmen, security officials and witnesses told Agence France Presse.

The man was found with his hands and feet bound and his head severed in the Sheikh Zuwayed area of north Sinai, they said.

Egypt's Prime Minister Hazem al-Beblawi said on Thursday he does not rule out posts for the Muslim Brotherhood in a new cabinet, if the candidates were suitably qualified.

Beblawi, who was appointed on Tuesday, said he was still considering who would comprise the interim government after Islamist president Mohamed Morsi's ouster in a popular military coup last week.

Gunmen on Wednesday opened fire on the car of a senior military commander in Egypt's restive Sinai peninsula, the army spokesman said, a day after two people died in an attack by militants on a security checkpoint.

The car of the second field army chief "came under heavy fire, which led to clashes between security forces and the terrorist elements," the spokesman said in a statement.