* Small al Qaeda-linked cell planned suicide attacks
* Armed groups have expanded into Sinai since uprising
* Arrested men had 10 kg of aluminium nitrate -minister
Egyptian have security forces thwarted a plan by an al Qaeda-linked cell to carry out a suicide attack on a foreign embassy, capturing three militants, the interior minister said on Saturday.
Mohamed Ibrahim said the men, who he accused of having links to militants in the Middle East and Pakistan, were found in possession of 10 kg (22 lb) of aluminium nitrate, which is used to make bombs.
He declined to say which embassy had been targeted.
"The Interior Ministry was able to direct a qualitative blow to a terrorist cell that was planning suicide operations against vital, important and foreign facilities in the country," he said in a televised news conference.
Egypt has long been an incubator for Islamist militancy. Al Qaeda's leader, Ayman al-Zawahiri, is Egyptian.
Security has deteriorated since a 2011 uprising that ousted President Hosni Mubarak, whose 30 years in power were marked by militant violence including an armed Islamist insurrection.
Armed Islamist groups expanded in the Sinai Peninsula after revolt, but militancy has been less apparent in the Nile Delta, where the majority of the population is concentrated.
Two of the suspects were from Alexandria on Egypt's Mediterranean coast, the state news agency reported. It did not say where the third was from.
It was the second time since President Mohamed Mursi, a Muslim Brotherhood politician, came to power that the authorities have said they had uncovered a militant Islamist group in the Nile Valley.
Twenty-six alleged Islamist militants including two former military officers went on trial last month for planning attacks against the state. Ibrahim said that group - known as the Nasr City cell - was connected to the militants whose arrest was announced on Saturday.
He said the militants had been in contact with a militant leader identified as Kurdi Dawud al-Assadi, whom he described as the head of al Qaeda in some countries in west Asia.
Assadi had instructed them to get in touch with members of the Nasr City cell and another militant group based in Sinai - where militants killed 16 Egyptian border guards in an attack last August, he said.
The state security prosecutor's office ordered two of the men detained for 15 days pending investigations. The third was ordered not to leave his house, state news agency MENA reported.
Ibrahim said one of the suspects had travelled to Pakistan and Iran to receive training, and was a member of al Qaeda in Algeria, where 37 foreign hostages were killed January when Islamist militants laid siege to a gas plant.
MENA said two of them had been to countries in northwest Africa and Mali to get "acquainted" with militants abroad.
Ibrahim said they were also in contact with al Qaeda in Pakistan and "elements responsible for receiving terrorist elements on the Turkish borders".
They had been found in possession of statements issued by al Qaeda in the Islamic Maghreb, he added.