TOKYO — Sony urged a dozen laptop computer makers around the world to recall more of its defective batteries Friday, the latest headache for the electronics company struggling to regain its luster as the world’s premier electronics brand.

With two recalls Friday, the number of lithium-ion batteries that are being replaced now stands at about 7 million worldwide, Sony spokesman Takashi Uehara said. He refused to estimate how much it would cost the company.

Two major Japanese electronics makers, Toshiba Corp. and Fujitsu Ltd., were the latest to tell customers to return laptop batteries that could overheat and catch fire. A day earlier, IBM Corp. and Lenovo Group issued a recall. Last month, it was Apple Computer Inc. and Dell Inc.

Dell, the world’s largest personal computer maker, also said Friday it is increasing the size of its recall by 100,000, to 4.2 million, after it received more information from Sony.

Toshiba is recalling 830,000 Sony laptop batteries, and Fujitsu later said it was recalling an undisclosed number used in 19 of its laptop models worldwide, company officials said.

The Toshiba recall involves its Dynabook, Qosmio, Satellite Portege and Tecra models, but regional breakdowns and dates of manufacturing weren’t immediately available, said Toshiba spokesman Keisuke Omori.

Fujitsu spokesman Masao Sakamoto said the company is recalling battery packs used in 19 models in two product lines — the FMV-BIBLO LOOX P and FMV-BIBLO LOOX T.

Sony has said the batteries could catch fire in rare cases when microscopic metal particles come into contact with other parts of the battery cell, leading to a short circuit. Typically a battery pack will shut down when there is a short circuit, but on occasion, the battery could catch fire.

Sony spokesman Uehara, however, said neither Toshiba nor Fujitsu have reported injuries or damage involving the battery problem, and Sony’s recall request Friday was to “reassure customers and remove their concerns about accidents.”

Friday’s announcements marked the first time Japanese laptop makers were caught up in Sony’s massive global battery recall.

It’s a major embarrassment for the Japanese electronics and entertainment powerhouse, which is in the midst of a major overhaul of its operations involving closures of plants and divisions and job losses.

While Sony said it was still trying to assess the extent of the damage and additional spending for the battery problem, the Japanese newspaper Asahi said that an initially estimated cost of 30 billion yen ($254.2 million) could balloon to twice as much.

Sony shares closed 0.83 percent lower at 4,780 yen ($40.51) on the Tokyo Stock Exchange on Friday.

Omori said Toshiba’s recall was in response to Sony’s request, and Toshiba had not found any cases in which the laptops were at risk of catching fire.

“But we wanted to assure and satisfy our customers,” he said.

On Thursday, IBM and Lenovo, the world’s third-largest computer maker, said they were seeking the recall of 526,000 rechargeable, lithium-ion batteries purchased with ThinkPad computers after one of them caught fire at Los Angeles International Airport this month.

In August, Apple Computer Inc. recalled 1.8 million batteries worldwide, warning they could catch fire.