The Associated Press on Wednesday saw dozens of soldiers emerge from helicopters in the Jahan area of Marib province, near where security officials say the kidnappers are holed up with their captives.
Other helicopters could be seen flying low through the mountains, apparently trying to spot the tribesmen.
Tribal elders, who had been negotiating with the kidnappers, said the Italians - taken captive on Sunday - were still being held somewhere in the vast Sirwah region of Marib province, about 120km northeast of the capital, Sana.
Showing its growing impatience with the standoff, the government stopped delivering water to communal tanks in the area on Tuesday, a government official told AP on condition of anonymity.
For his part, Abdul-Kader Bajammal, the Yemeni prime minister, declared the government would strike hard against the kidnappers, whom he called terrorists.
Yemenis have protested against
An Interior Ministry official had told AP the army was about to launch an attack against the kidnappers, but aside from increasing the number of soldiers on Wednesday, there were no other signs of an imminent assault.
The Italian government continued to ask Yemeni authorities not to attack, fearing the tribesmen holding the three women and two men would kill their hostages.
Mario Boffo, the Italian ambassador to Yemen, told the Ansa news agency that negotiations were continuing and "contacts with the Yemeni government are very intense".
He said Rome and Sana authorities were in "substantial agreement and above all there's the common, very strong desire to end this in a positive way".
Boffo told Ansa the hostages were in good condition.
Earlier, Boffo told Aljazeera from Sana: "The message from our government is that I've told the Yemeni government that we are against any action that would put our kidnapped citizens in danger.
"And the Yemeni government has assured me they would not do anything that would endanger the hostages."
Talks to free the five were deadlocked over the kidnappers' refusal to drop their demand that fellow tribesmen be freed from prison in exchange for the Italian tourists.
Within hours of the Italians' abduction on Sunday, negotiators persuaded the kidnappers to free the three women. The women, however, refused to leave until their companions also were released.
Patrizia Rossi, one of the five
kidnapped Italian tourists
Meanwhile, a thousand Yemeni protested in the street of Marib city demanding the government punish the kidnappers.
Last week, a former German Foreign Ministry official and his family were freed after a four-day kidnapping ordeal in the east of Yemen.
Tribesmen of the poor country at the southern tip of the Arabian peninsula often resort to kidnapping tourists to force concessions from the government.
Hostages normally have been released unharmed, but several were killed in 2000 when Yemeni soldiers carried out a botched raid to free them.
Government control in regions outside major population centres in Yemen is tenuous.