Kolkata - The Indian police have arrested two men accused of providing cellphone SIM cards to the gunmen in the Mumbai attacks, the first known arrests in the probe since the siege ended.

The police said yesterday that they had arrested the two men, identified as Tausif Rehman and Mukhtar Ahmed, on Friday after investigators traced some of the SIM cards recovered from the gunmen.

'We are questioning them about procurement of SIM cards used in Mumbai,' Mr Jawed Shamim, the deputy commissioner of detectives in Kolkata, told Reuters.

The arrests were further evidence of Indian complicity in the three-day rampage that Indian officials have blamed on Islamic militants from neighbouring Pakistan. The incident has raised tensions between South Asia's long-time foes, both of which have nuclear weapons.

Tausif, a clerk, used a dead relative's identity documents to acquire the 22 SIM cards which he later sold to Mukhtar, Mr Jawed said. Both men were charged with conspiracy and forgery.

Mukhtar was a street vendor and taxi driver in Kolkata. He was arrested in New Delhi.

Mr Jawed said it was not immediately clear how the SIM cards were passed to the gunmen, whom investigators have said used cellphones 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 group blamed for earlier attacks in India.

The group is on United States and Indian terrorist lists, and Indian police say two of its operation 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 hit in the attack.

At least 171 people were killed in the attacks 11/2 weeks ago, 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 yesterday, with extra security personnel deployed after India's civil aviation authority said it had received intelligence that attacks could be planned.

In a related development, it was 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, two days after the attacks on Mumbai began.

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 Dawn newspaper in Pakistan said, citing unnamed political, diplomatic and security sources.

The episode triggered intense international diplomacy, with some world leaders fearing that India 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.

Meanwhile, a huge bomb blast ripped through a crowded marketplace in north-west Pakistan, killing 27 people, police said yesterday.

An explosives-laden car blew up in a busy shopping area on Friday in the city of Peshawar, ahead of the Muslim festival of Eid, destroying shops and hotels.

Reuters, AP, AFP