Palestinians reported heavy fighting in Jenin and Jericho
Palestinian officials said Israeli forces had killed three Palestinians and wounded 11 in overnight clashes in Jenin.
Israeli tanks had also rolled into the Palestinian-controlled town the previous night. At least seven Palestinians were reported killed in the earlier clashes.
Despite the violence, there are signs that the long anticipated meeting between Palestinian leader Yasser Arafat and Israeli Foreign Minister Shimon Peres may take place in the next few days.
Mr Peres has said there is now a tentative agreement on where and when to hold the talks.
The news follows a telephone call to both sides by US Secretary of State Colin Powell on Wednesday.
But BBC Jerusalem correspondent Caroline Hawley says that even if the talks go ahead in the current poisoned atmosphere, there is absolutely no guarantee of success.
Heavy fighting
Palestinian officials said Israeli forces attacked a local government building in Jenin on Thursday.
Heavy fighting was also reported further south in Jericho, where Palestinian officials said some 20 Israeli tanks accompanied by bulldozers made an incursion.
Loudspeakers on mosques called people out to defend the town against the invading Israeli forces, witnesses said.
The Israeli army said it had no comment on the reported incursion into Jericho.
"There is fierce resistance to the Israelis. The tanks are moving towards Palestinian headquarters, where all the Palestinian security offices are located," said Palestinian cabinet minister Saeb Erekat, a Jericho resident.
'Connected to US attacks'
Mr Erekat drew a connection between the incursions and the terror attacks in New York and Washington on Tuesday that destroyed the World Trade Center and damaged the Pentagon.
"The Israelis are using the tragedy of the events in New
York and Washington, feeling that the attention of the
world is elsewhere," he said.
It was not immediately clear what the purpose of the latest Israeli incursion was, but the presence of the bulldozers indicated that they intended to tear down Palestinian structures.
The main official Palestinian buildings in the town are an old military base used as police headquarters and a prison.
Suicide bombers
Israel says Jenin has been a breeding ground for suicide bombers.
The Israeli prime minister's office called the town "a hornet's nest" from where it said at least six suicide bombing missions had been carried out since the Palestinian uprising began last September.
Israel says a suicide bomber who blew himself up in the Israeli coastal town of Nahariya on Sunday, killing three Israelis, had been trained by a Hamas cell based in Jenin.