Earlier on Monday, Abdul Hakim Awad, a Fatah spokesman, said two Fatah members had been abducted by Hamas gunmen in Gaza City and Hamas said that one of its officials has been seized in Ramallah.
While both sides have released some hostages taken during the fighting, officials said before the Force 17 incident that Hamas still held nine Fatah men while 32 members of Hamas remained in Fatah custody.
Khaled Meshaal, the exiled political leader of Hamas, Ismail Haniya, the Palestinian prime minister from Hamas, and Mahmoud Abbas, the Palestinian president and Fatah leader, are all due to attend the talks hosted by Saudi King Abdullah.
The talks are seen as a last-ditch effort to reach a power-sharing agreement and end the factional fighting that has killed 63 Palestinians since January 25.
Negotiators have tried but failed for months to find common ground on the key issues of ties with Israel and the division of portfolios in a unity accord, in the hope of ending a boycott by the US and EU.
Washington and Brussels consider Hamas to be a terrorist group and suspended direct financial aid to the Palestinians when the current Hamas-led cabinet took power in March.
"It is pitiful to witness the bloody scenes in Gaza between the brothers"
The Hamas-led government has resisted pressure to renounce violence, recognise Israel and abide by peace deals between the Palestine Liberation Organisation (PLO) and Israel.
Haniya on Monday took his lead from Meshaal in declaring that there could be no other possible outcome but success, despite months of failed meetings and collapsed ceasefire deals.
He told his cabinet meeting in Gaza City: "There may be obstacles but we confirm that we are going with true intentions to reach a Palestinian-Palestinian agreement that would end tensions and reinforce national unity.
"We have no choice but to reach an agreement."
Meshaal told a news conference in the Syrian capital, Damascus, on Sunday: "We want a true partnership between Fatah and Hamas. We are in the same boat. There is no other way to strengthen national unity."