* Detained men helped attackers with mobile phone cards
* Pakistan went on alert following hoax call-report
* Indian airports on alert for a fourth day
By Tamajit Pain
KOLKATA, Dec 6 (Reuters) - Indian police said on Saturday that they had arrested two men who helped the Mumbai attackers get mobile phone cards they used to stay in touch during the three-day rampage.
Police in the eastern city of Kolkata said they had arrested two men they identified as Tausif Rehman and Mukhtar Ahmed on Friday after investigators traced some of the Subscriber Identity Module (SIM) cards recovered from the gunmen.
"We are questioning them about procurement of SIM cards used in Mumbai," Jawed Shamim, the deputy commissioner of detectives in Kolkata, told Reuters.
The arrests are further evidence of Indian complicity in the three-day rampage New Delhi has blamed on Islamic militants from neighbouring Pakistan, which has raised tensions between South Asia's longtime foes, both of which have nuclear weapons.
Rehman, a clerk, used a dead relative's identity documents to acquire the 22 SIM cards, which he later sold to Ahmed, Shamim later said. Both men were charged with conspiracy and forgery.
Ahmed was a street vendor and three-wheel taxi driver in Kolkata, Shamim said. He was arrested in New Delhi.
Shamim said it was not immediately clear how the SIM cards were passed to the gunmen, whom investigators have said used the phone to stay in touch with their controllers in Pakistan during the 60-hour rampage.
Mumbai police have said the gunmen were controlled by the Pakistan-based Lashkar-e-Taiba (LeT) group blamed for earlier attacks in India.
LeT is on U.S. and Indian terrorist lists and Indian police say two of its operations leaders, who were designated terrorists by Washington in May, coordinated the Mumbai rampage.
In February police arrested an Indian citizen, Faim Ansari, who was carrying maps of Mumbai that highlighted several of the targets later hit in the attack.
At least 171 people were killed in the attacks last week in which 10 gunmen struck two luxury hotels and other landmarks across India's financial capital.
Airports in New Delhi, Bangalore and Chennai remained on high alert for a fourth day on Saturday, with extra security personnel deployed after India's civil aviation authority said it had received intelligence that attacks could be planned.
Also on Saturday, Pakistan's Dawn newspaper reported that Pakistan put its forces on high alert after a hoax caller pretending to be India's foreign minister spoke to President Asif Ali Zardari threateningly on Nov. 28. [nISL383109]
That was two days after the attacks on Mumbai began.
"It's true," a diplomat with knowledge of the exchanges told Reuters when asked if the newspaper report was correct.
Throughout the next 24 hours Pakistan's air force was put on "highest alert" as the military watched anxiously for any sign of Indian aggression, the newspaper said sourcing its report to unnamed political, diplomatic and security sources.
Dawn said that the caller, posing as Indian Foreign Minister Pranab Mukherjee, also tried to telephone U.S. Secretary of State Condoleeza Rice, but due to specific checks by U.S. officials the call was not put through.
The episode triggered intense international diplomacy, with some world leaders fearing that Indian and Pakistan could slip into an accidental war, the newspaper said.
There is an ongoing investigation by both sides to determine who made the call, and it remains unclear whether it was made from India or Pakistan, the newspaper said.
Pakistani officials said the caller ID was a Delhi number, but Indian officials have said the number could have been manipulated. (Reporting by New Delhi, Mumbai and Islamabad bureaux; Writing by Bryson Hull; Editing by Sanjeev Miglani)