Hamas issued an ultimatum today to those holding BBC journalist Alan Johnston in Gaza, threatening to free him by force if they don't release him by the end of the day.
"If he is not released, we would use all means to secure his life and to free him," a senior Hamas official said of Johnston, who was abducted in Gaza on March 12.
Meanwhile, Israel, the transit point for goods entering the Gaza Strip, ordered cargo shipments bound for the Hamas-controlled territory blocked, the Israeli customs authority said in a letter.
But officials said shipments to Gaza, an impoverished enclave almost entirely dependent on imports and international aid, may be allowed to go through at a later date.
"Given recent developments in the Gaza Strip and the closure of crossings between it and Israel, I hereby inform you that no cargo destined for the strip is to be released until further notice," an Israeli Finance Ministry official in charge of customs told Israeli customs agents in the June 17 letter.
A spokesperson for Israel's tax and customs authority said the order was issued because crossings into Gaza have been closed, calling it "a technical steps, not a policy decision."
Earlier, Palestinian President Mahmoud Abbas's emergency cabinet, bolstered by Western promises to resume aid, vowed today to exert its authority over the Hamas-controlled Gaza Strip.
"The government will pursue its jurisdiction over all parts of the homeland, regardless of what happened in Gaza," Mr Abbas's Information Minister Riyad al-Malki told reporters after the new government met in the West Bank town of Ramallah.
Mr Abbas formed the new cabinet last week in the West Bank after the Hamas Islamist group's armed wing routed security forces dominated by his Fatah movement in Gaza.
It is unclear how much influence Abbas's government can have in Gaza, now a Hamas fiefdom. Gaza and the West Bank are separated by 30 miles (45 km) of Israeli territory.
Mr Abbas's forces are focused on trying to prevent any spillover of the fighting from Gaza to the West Bank, where Fatah holds sway under Israeli occupation and where Hamas has threatened reprisals.
"We still do not have a clear plan," Mr Malki said.
Asked how he would enforce the law in violence-prone Gaza, Mr Abbas's interior minister in charge of security, Abdel-Razzak Yahya, said: "I swear to God I do not know."
Ismail Haniyeh of Hamas has said he still considers a three-month-old unity coalition in which he is prime minister as the legitimate Palestinian government and accuses Mr Abbas of participating in a US-led plot to overthrow him.
The European Union said today it wants to resume direct aid to the Palestinians, but did not say when funds would be freed up.