Egypt said on Saturday it was expelling Turkey's ambassador and accused Ankara of backing organisations bent on undermining the country - an apparent reference to the Muslim Brotherhood of ousted Egyptian president Mohamed Mursi.
Turkish Prime Minister Tayyip Erdogan, himself a supporter of an Islamist-led government forced from power by generals in 1997, issued a blunt rebuff to Egypt's army-backed rulers, declaring on live television: "I will never respect those who come to power through military coups."
He spoke shortly after Turkey had retaliated to the Egyptian move by declaring the Egyptian ambassador, currently out of the country, persona non grata.
Egyptian foreign Ministry spokesman Badr Abdelatty made no specific allegations against Turkey in announcing the ambassador's expulsion, but said: "(Ankara is) ... attempting to influence public opinion against Egyptian interests, supported meetings of organisations that seek to create instability in the country."
Turkey has emerged as one of the fiercest international critics of Mursi's removal, calling it an "unacceptable coup" by the army. Mursi's Muslim Brotherhood, which has been staging protests calling for his reinstatement, has close ties with Erdogan's AK Party.
Turkish President Abdullah Gul speaking on state-run TRT television before Erdogan, was more measured in his remarks.
"I hope our relations will again get back on track," he said.
Both countries will remain represented in each other's capitals by embassies headed by a charge d'affaires, effectively a number two.
Both had recalled their ambassadors in August for consultation after Egyptian security forces stormed into pro-Mursi camps on August 14, killing hundreds.
In some of the worst civilian violence in decades, security forces crushed protests by Mursi's supporters. Militant Islamists, who have been attacking Egyptian forces in the Sinai peninsula, stepped up their assaults in or near major cities.
Relations deteriorated between Egypt and countries that criticised Mursi's ouster and the government crackdown on the Brotherhood where thousands have been arrested.
Qatar, once a major ally to Egypt under Mursi which lent or gave Egypt $7.5 billion, condemned the security forces crackdown against the Brotherhood in August. Egypt described the statement as an interference in its affairs.
In September, Egypt returned a $2 billion Qatari deposit with its central bank after talks to convert the funds into three-year bonds broke down.
Egypt's army-backed interim government is implementing what it calls a roadmap to democracy that could see fresh elections by early next year.
In comments underlining the government's stance against the Muslim Brotherhood Interior Minister Mohamed Ibrahim, on Saturday, accused them of supporting and financing extremists with the goal of causing instability in Egypt.
In a half hour press conference Ibrahim named groups and individuals that he accused the Muslim Brotherhood of mobilizing. He linked some of them to al-Qaeda and 'other extremist groups from the Gaza strip', in a reference to Hamas.
Ibrahim said security forces arrested five individuals from al-Qaeda linked groups who were present at the pro-Mursi vigils in Cairo before they were dispersed on August 14. The Brotherhood denies any links to violence.
Ibrahim said security forces found documents, seized weapons, and foiled various attack attempts against public figures, police and army personnel. It also blamed those groups for attacks against the police and army since June 30.
Leaders of the Muslim Brotherhood, including Mursi, are currently in detention facing charges of inciting violence.
To commemmorate the passing of 100 days since security forces cleared the pro-Mursi vigils in Cairo, supporters of the Muslim Brotherhood plan to take to the streets on Sunday.
But Ibrahim warned protesters they would be dealt with firmly. "From now on any protest that disrupts roads, any protest that is not peaceful, I will deal with it firmly and decisively no matter what the losses are to me or to them."