Palestinian President Mahmoud Abbas underwent an unannounced heart test at a Jordanian hospital on Thursday, adding new uncertainty to already troubled peace talks.

Aides to Abbas, 73, said he was doing well after a catheterization procedure they described as successful, and that he was expected to leave Jordan Hospital later in the day. Abbas is due to return to the West Bank on Friday, they said, adding that they expect him to return to work immediately after his arrival.

In the Gaza Strip, Thursday, Israeli aircraft sent missiles slamming at a group of Hamas militants, killing a gunman involved in the capture of an Israeli soldier two years ago, the Israeli military said. The death threatened to cloud Egyptian-led efforts to broker a truce in Hamas-ruled Gaza.

In a separate incident, Palestinian medical officials said a 62-year-old civilian was killed and three militants wounded by Israeli fire, during fighting near the southern Gaza town of Khan Younis. The military said there had been exchanges of fire in the area but could not immediately give further details.

In Amman, Abbas spokesman Nabil Abu Rdeneh said a doctor recommended the catheterization procedure during a routine medical examination Thursday.

Saeb Erekat, a top aide to Abbas, said he spoke to the Palestinian leader from the West Bank on Thursday afternoon. "He's doing very very well. He's in very high spirits. He even joked to me," Erekat said.

He said Abbas planned to resume his schedule immediately and has meetings scheduled with U.S. Secretary of State Condoleezza Rice on Sunday and with Israeli Prime Minister Ehud Olmert sometime next week.

Israeli officials had no immediate comment on Abbas' test.

Palestinian officials initially said Abbas underwent an angioplasty, a treatment to help open blocked arteries. But later, they said the procedure was only a catheterization to check for blockage. The Arabic word "castara" is used to describe both procedures.

In cardiac catheterization, a doctor inserts a thin plastic tube into an artery or vein in the arm or leg, and from there advances it into the chambers of the heart or into the coronary arteries. The test can measure blood pressure within the heart and how much oxygen is in the blood. It's also used to gather information about the heart muscle's ability to pump.

Abbas underwent a similar procedure in 2005, and had prostate surgery in the U.S. in 2001.

It was not clear how Abbas' health problems would affect peace talks, if at all. Dr. Victor Guetta, deputy director of the heart institute at Sheba Medical Center in Tel Aviv, said patients can go back to work immediately after the procedure.

The negotiations are secret, and while some insiders claim progress, the situation on the ground remains largely unchanged.

Israel continues to build homes on land the Palestinians claim for a future state, and movement in the West Bank remains severely restricted by Israeli military roadblocks, stifling the Palestinian economy.

Israel says the roadblocks are needed to halt militants. It says Abbas has not reined in militant groups in the West Bank. His government also has no authority in the Gaza Strip, which has been ruled by a rival government of Islamic Hamas militants since June.

Abbas traveled to Washington last week hoping to get a boost for his efforts, but returned disappointed and pessimistic about achieving any deal with Israel this year. The two sides have set a year-end target for a peace agreement since relaunching peace talks last November.

While pursuing peace with Abbas, Israel continues to pursue Gaza militants involved in attacks on Israel.

Hamas confirmed that a "leading commander" was killed in an Israeli airstrike in southern Gaza on Thursday, and its military wing vowed to avenge the death of Nafez Manzur.

"The blood of our late commander will not be shed in vain," the statement read. "We have the full right to respond in the time and place that we choose."

Israel said Manzur was involved in the capture of Cpl. Gilad Schalit, an Israeli soldier seized in June 2006 after militants from Hamas and two allied factions tunneled under the Israeli border and attacked a military post. Two other soldiers were killed in that raid.

Schalit remains in captivity in Hamas-ruled Gaza as talks have stalled on swapping him for hundreds of Palestinians held in Israeli prisons.

The military did not say whether Manzur was involved in the actual capture of Schalit, or whether he took part in the planning. Hamas did not confirm whether Manzur was involved in Schalit's capture.

The deadly airstrike came as Egypt tries to broker a cease-fire in volatile Gaza, where militants launch near-daily rocket and mortar attacks on southern Israel, provoking Israeli reprisals.

The deal Egypt is trying to put together includes a six-month truce, a prisoner swap and the opening of Gaza's border crossings.

The Israeli government shuns Hamas because of its commitment to Israel's destruction, and Israeli officials have not acknowledged involvement in the truce efforts. Publicly they say Hamas is interested in a truce to buy time to rearm after harsh Israeli military operations.

Israel sealed its border with Gaza after Hamas seized control there in June. It says it worries that lifting the blockade would allow militants to rearm.

Israel has also rejected the lists of prisoners Hamas wants freed, saying they include hundreds of militants involved in attacks on Israel.

Last week, Hamas said it would accept a six-month cease-fire with Israel, provided Israel ends the economic blockade, which has caused shortages of basic items and deepened unemployment in the impoverished territory. Twelve smaller factions approved the deal on Wednesday, with some reservations.