Palestinian security forces are continuing their search for an Egyptian diplomat abducted by gunmen in Gaza City on Thursday.
Security has been stepped up at the Egyptian mission in Gaza
Hussam al-Musali, Egypt's military attache, was stopped on his way to work and forced into vehicle.
Palestinian militant groups have condemned the kidnapping as a "cowardly act" that has threatened Palestinian relations with its important neighbour.
Foreigners are frequently kidnapped by gunmen in Gaza.
The hostages are generally held for a short time to press the authorities for money, jobs or prisoner releases.
The BBC's Alan Johnston in Gaza says there are suspicions that this latest abduction - the first of a diplomat - may have more political overtones. Egypt has significant influence in Gaza.
A statement issued by the al-Nasir Salah al-Din Brigades, the armed wing of the Popular Resistance Committees, said the abduction was a "cowardly act" carried out by "irresponsible groups who tamper with the people's relations with their Arab brothers".
The group called on the Palestinian Authority to "mete out the severest punishment" to the perpetrators "so that they become a lesson to others".
A spokesman for Hamas, the victorious party in last month's parliamentary elections, expressed the group's "extreme indignation at this crime" and stressed that "those who commit such acts aim to harm our people and mar the excellent relations between the Egyptian and Palestinian peoples".
A statement posted on a website affiliated with Islamic Jihad denounced the kidnapping and called for his immediate and unconditional release.
The group praised Egypt's role in the Palestinian territories and called for an "end to lawlessness and the kidnapping of foreigners and Arab friends".
On Thursday, Palestinian President Mahmoud Abbas instructed security services to act "immediately to arrest those responsible and bring them to justice".
But a spokesman for the Palestinian Interior Ministry said the search had so far been fruitless.
"Until now we have no clues that could lead us to the kidnappers," Tawfiq Abu Khusa told the AFP news agency.
"We hope to be able to arrest them as quickly as possible and put an end to this matter."
No group has said it was behind the abduction, and the Palestinian authorities have not been contacted with demands.
Egypt's Foreign Ministry said it was working to "expedite the release of the kidnapped diplomat".