But the new arrivals are bound to be disappointed, as the opportunity to become legal is tightly restricted to those already living here. Since July, the Spanish authorities have picked up more than 1,000 North Africans trying to cross the Gibraltar Strait in rickety wooden fishing boats. Up to 2,000 undocumented immigrants have been held so far this year, the highest for four years.
In recent weeks, pathetic boatloads of would-be immigrants have been plucked almost daily from Spain's southern waters. Thousands more are thought to have eluded the authorities and entered unseen. Many do not survive the hazardous crossings.
The number this year has risen on account of the immigrants' expectation that if they reach Spain before today, they will be able to regularise their illegal status. This is the promise being touted by unscrupulous mafia gangs operating in northern Morocco who charge up to pounds 800 for a perilous passage. Many hopefuls are scrambling to "jump the Strait", believing that this will be their last chance to enter Europe. Most of them will be detained and deported.
Today's deadline allows only those who were already resident in Spain before 1 January 1996, and in possession of a work permit, to apply to regularise their situation. It is the fruit of an agreement in February to modify Spain's restrictive Foreigners' Law of 1985.
Trade unions say the objective was to improve the conditions of legions of immigrant workers by allowing those whose work permits had expired to renew them. So far 13,000 have applied, but the immigration spokesman for the Workers' Commissions union, Francisco Soriano, says up to 50,000 foreigners who lost their work permits are eligible, even under the interior ministry's restrictive terms.
Queues have been stretching round police stations all this week as immigrants without documents, often long resident in Spain, seek to put their papers in order. The government said it would not extend the deadline, despite pleas from trade unions, which fear that many will never reach the head of the queue in time.
Experts say the flow of migrants will continue. "It is no good harassing immigrants like common delinquents, as if they had committed a crime," says Julio Martinez Firvida, of the immigrants' support organisation in Algeciras. "They are only trying to escape a desperate situation in their own countries. Tighter controls won't solve anything."
Mr Soriano says the regulation will do nothing to improve the condition of thousands of illegal workers who cannot claim social security and who remain under the constant threat of being reported to the authorities. Officials hesitate to put a figure on the numbers of illegal immigrants in Spain - most of whom are Moroccans, followed by Latin Americans, Poles and Chinese - but unofficial estimates range up to 200,000.
A growing number of Central Africans are trekking north and entering Europe's southern border at Spain's Moroccan enclaves of Ceuta and Melilla. In June more than 100 Central Africans who had reached Melilla were flown to Madrid and expelled, under sedation, within hours.
The operation was criticised by human-rights groups for its disregard for democratic procedures. The UN human rights commissioner, Jose Ayala Lasso, last week warned the Spanish government "not to commit the error of applying methods alien to human dignity in controlling immigration".
Within days of the Central Africans being flown out of Melilla, scores more had entered the enclave to replace them.Reuse content