Hamas gunmen on Tuesday took up positions around the stronghold of the shadowy group holding kidnapped British journalist Alan Johnston.
Members of Hamas' 6,000-strong militia moved onto rooftops of high-rise buildings and deployed gunmen in streets in the Gaza City neighborhood inhabited by the Doghmush clan. The large, heavily armed family leads the Army of Islam, a little known group that has been holding Johnston for nearly four months.
In an afternoon exchange of fire, a Palestinian civilian was killed, Hamas said, blaming the Doghmush forces. No other casualties were reported.
"The clocks have begun ticking toward the release of Alan Johnston," said Hamas spokesman Ghazi Hamad. "The operation of the interior ministry Executive Forces has started, and they are tightening the siege on the people involved in his kidnap."
Late Tuesday, the Doghmush clan released nine students loyal to Hamas that they kidnapped earlier in the week. Hamas officials and mediators said the release was meant to pave the way for Johnston's release. However, they did not know if or when Johnston would be released.
Earlier, Interior Ministry spokesman Khaled Abu Hilal of Hamas said security forces "will not spare any efforts to free the British journalist." Hamas radio also broadcast a toll free phone number, urging people to call in any information about the case. Witnesses said at least four members of the Doghmush clan were detained by Hamas.
Since seizing control of Gaza last month, Hamas has demanded Johnston's release in an apparent bid to gain favor with the West.
Hamas spokesman Fawzi Barhoum accused Johnston's captors of smearing the Palestinian people's reputation and of seeking "to prove to the world that we are a group of militias that fight each other to gain personal ends."
Independent Muslim clerics made efforts to reconcile the two sides, but the Army of Islam said Hamas did not respond. Hamas, whose militiamen were in the streets checking for guns, had no comment on the efforts.
The Army of Islam, whose formerly close relations with Hamas have soured, has demanded that Britain first release a radical Islamic cleric with ties to al-Qaida. It also has threatened to kill Johnston if Hamas tried to free him by force.
On Monday, Hamas arrested the spokesman of the Army of Islam, giving it a potentially valuable bargaining chip in its efforts to release Johnston.
Johnston, who was kidnapped on March 12, has been held far longer than any Western journalist abducted in Gaza. Hamas has said it knows where to find him, but has not raided the hideout for fear he will come to harm.
Last week, the Army of Islam posted a video message from Johnston on a militant Web site in which he appeared to be wearing an explosives belt that he said his captors would detonate if there was an attempt to free him.
The same group was involved in the capture of Israeli Cpl. Gilad Shalit, who was seized more than a year ago in a raid on an Israeli army post near Gaza.