Police in the eastern city of Kolkata identified the men as Tausif Rehman and Mukhtar Ahmed and said they were picked up 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, 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 the attacks on Islamic militants from neighboring Pakistan, raising tension between South Asia's longtime foes, both nuclear-armed.

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.

Security was also high in the north Indian town of Ayodhya on Saturday, the 16th anniversary of the razing of the Babri mosque by a Hindu extremist mob which set off Hindu-Muslim riots that killed thousands. A makeshift Hindu temple now stands there.

Hindu nationalists burned five Pakistani flags in front of the temple site on Saturday to shouts of "Down with Pakistan!"

"We decided to also condemn the terror unleashed by Pakistan on our country," a spokesman for the group, Sharad Sharma, said. "And what could have been a better way to condemn than setting ablaze the flags of that country?"

At least 700 extra officers were protecting the site, district police chief R.K.S. Rathore told Reuters.

Earlier, 15 Hindu activists demanding a permanent temple be built were arrested in nearby Faizabad while Muslim activists who ordinarily fly a black flag on the anniversary opted not to.

"We are not making any public protest this time in view of the large-scale carnage by terrorists in Mumbai," activist leader Yunus Siddiqui told Reuters.  Continued...