Rebels in eastern Chad have stepped up their campaign to overthrow President Idriss Deby, leading a week of attacks that have raised concerns among aid organizations.  With less than a month to go before presidential elections the opposition has promised to boycott, experts say the country is entering a dangerous period.

Embassies in Ndjamena are on high alert, and government forces are reinforcing security in the capital as fighting between the army and rebels creeps closer to the Chadian capital.

The latest wave of attacks by the rebel United Front for Change, began Sunday, says Chadian journalist Evariste Ngaralbaye.

He noted that the rebels launched offensives in the southeast of Chad and since Tuesday, there have been attacks in the center of the country around 400 kilometers to the south of the capital, Ndjamena.

Front leaders have vowed to take the capital and topple President Deby before a presidential election set for early May.

Journalist Ngaralbaye adds that Chadians in Ndjamena are worried, both for the overall security situation and the possible impact on the election.

"We are all waiting to see if the government forces will get the upper hand, waiting to see if the elections will actually take place at all," he said.

Until now, fighting had been largely confined to a lawless area along Chad's border with Sudan.  The government claims rebels launched attacks from bases within Sudan's western Darfur province.

But this week's attacks mark an increase in the level of fighting between government forces loyal to the president and the rebels who have been fighting to overthrow him since late last year.

The lack of security in the countryside, says a Chad expert with the U.K.-based analysis firm Oxford Analytica, Richard Barltrop is not the only obstacle to elections.  The major opposition parties have vowed to boycott the vote.

"Its possible that the elections would be carried out," he said.  "But if the elections were to go ahead, then they would almost certainly be judged unsatisfactory by properly independent monitors."

But Barltrop says the polls are likely to be postponed, as the rapid deterioration of the security situation in Chad has forced President Deby to face the more serious problem of his political survival.

"The range of scenarios that were on the table for Chad were, firstly, the possible collapse or overthrow of the government by rebel groups," he added.  "Secondly, a continuation of the status quo.  And the third scenario is, what you could say, stabilization and improvement in the situation.  With these latest developments, you can put that third scenario off the table.  You can forget about it."

And Barltrop says even maintaining a status quo where Mr. Deby retains power with minor uprisings in the outlying provinces is becoming more and more difficult as well.

A wave of army desertions gripped Chad last year, creating recruits to several of the rebel groups that now make up the United Front for Change.  President Deby dissolved his elite Republican Guard, but defections to the rebels among high-level officers continued.

"Right at the moment, I would put it at more than 50-50, odds on in favor of the government being toppled," he said.

Chad's government has accused neighboring Sudan of backing the rebels, a charge Khartoum denies.

President Deby came to power at the head of an insurgency, which launched a successful bid from Sudan to topple Chad's then-leader, Hissene Habre, in 1990.