Israeli tanks on Tuesday entered the eastern area of the Gaza Strip and troops clashed with Palestinian fighters there, wounding at least three militants, witnesses and Palestinian sources said.
The Israeli army said it was checking the report.
Witnesses said several Israeli tanks, supported by unmanned drones in the sky, entered Gaza near the Karni crossing, the main terminal for goods entering and leaving the densely populated strip, but it was not clear what their objective was.
Clashes ensued and three militants were wounded, Palestinian sources said.
Israel has carried out repeated brief incursions into Gaza over the past six weeks, since launching an operation in late June to rescue a soldier captured by Palestinian militants and to stop rocket fire from the strip into Israel.
Earlier separate Israeli air strikes targeted houses in Jabalya, a district of Gaza City, in the northern part of the strip, and the southern Gaza town of Rafah, but there were no immediate reports of any casualties or damage.
Witnesses said residents had been warned to leave the buildings ahead of the strikes, which they said appeared to target the homes of members of Hamas and Islamic Jihad, two militant groups.
Gaza, a narrow coastal piece of land that is home to 1.4 million Palestinians, was occupied by Israeli troops until August last year, when soldiers and about 8,000 Jewish settlers pulled out after nearly 40 years of occupation.
A week ago, armed men kidnapped two journalists from the Fox TV network, an American and a New Zealander, as they were working in Gaza City. There has been no word on their whereabouts or any claim of responsibility for the act since.
While kidnappings have not been uncommon in Gaza in recent years, most abductions are resolved in a matter of hours without any harm being done.