"Beware the outsider," reads a poster stuck to a wall near Tahrir Square in Cairo. "Don't open your heart to him, you don't know who he is," another warns.
A week after Egypt's elected president was ousted by the military, excitement among those calling for his downfall is turning to distrust. Some are now blaming fellow Arabs from other countries for the violence that has followed.
Deadly clashes between ousted leader Mohamed Morsi's supporters and the army have stoked paranoia that trouble is being stirred up by outsiders, especially from Syria and Gaza, home to Islamist groups seen as close to Morsi’s Muslim Brotherhood.
"Syrians, Palestinians, Israelis, you can find them on every street corner. They're here to exploit the chaos," said Yusuf Al-Desouki, waiter at a busy coffee shop in downtown Cairo.
"Yeah!" chimed in 21-year-old customer Mohammed al-Nahsi. "I heard two Palestinians on the metro — they were hatching a plan against the military."
A flurry of media reports and government assertions that foreigners have infiltrated Egypt and are taking part in violence have helped sow widespread distrust.
Accusations of foreign meddling during domestic crises are not new and were common under ex-president Hosni Mubarak.
Just a month before Mubarak's government was ousted by mass demonstrations, the interior ministry blamed a January 2011 bombing of a church in Alexandria that killed 24 Coptic Christians on a Gaza-based group "Army of Islam."
No evidence was produced, and many Egyptians believe the attack was in fact plotted by Mubarak's security forces.
'Making it up'
Since Morsi's overthrow, the paranoia has returned with new force.
Uncorroborated news reports and outspoken pundits paint a picture of nefarious foreign hands at work. Washington has also been named in the media as a conspirator.
Authorities have deported hundreds of Syrians arriving at Cairo Airport after tightening visa requirements, which the foreign ministry said was aimed at limiting "jihadist elements" from moving from Syria to Egypt.
A state prosecutor said on Sunday that five Syrians arrested on suspicion of shooting at an anti-Morsi rally admitted to receiving money and arms from the Muslim Brotherhood.
On Monday the interior ministry issued a statement banning foreigners from joining street protests.
"All those aggressors interfering in the internal affairs of Egypt can go to hell. All those defending them can go to hell too," Youssef el-Hosseiny, a popular radio and television presenter, said on his Twitter account on Thursday.
Media magnate Tawfiq Okasha told his television viewers on Thursday that Egyptian citizens should form a "defense army" and arrest Syrians, Palestinians and Iraqis causing trouble.
"We have not and we will not take a side in the political crisis on the Egyptian street," said a Syrian community group representing the émigrés in Egypt opposed to President Bashar al-Assad in that country's bloody civil war.
There are around 70,000 Syrian refugees registered with the United Nations living in Egypt.
"Our presence is temporary, lasting until the moment we can return to a free Syria," the group said in a statement.
Smarting from their loss of power after more than 80 years of street-level organizing, the Muslim Brotherhood says the accusations against outsiders are part of a "fear-mongering" campaign by the new government aimed at diverting attention from its own difficulties.
"The army wants to cast itself as defending Egypt from foreign subversion," said Gehad al-Haddad, a spokesman for the Islamist movement. "They are making this up as they go along."