Thimphu, Apr 28 (IANS): The case of spying by an Indian woman diplomat at the Indian High Commission in Islamabad was a "serious issue", External Affairs Minister S.M. Krishna said here Wednesday. Pakistan also reiterated that it was an "internal matter" of India.

"Investigations are going on. We will have to wait till the investigations are complete and then find out what was the motive and what was the modus operandi," Krishna told reporters in the Bhutanese capital, where regional leaders have gathered for the South Asian Association for Regional Cooperation (SAARC) summit.

"It is a serious issue. That's the reason why she was called back and is now under police custody," he added, a day after second secretary Madhuri Gupta was remanded to police custody on charges of spying for Pakistan's spy agency ISI.

"MHA (ministry of home affairs) is doing the investigation. Once we get all the reports, what needs to be done will be done by the government of India," the minister said.

The Pakistan foreign office also reiterated that the issue was an "internal matter" of India. The spokesperson told reporters here that they had only learnt about the matter from media reports and that there was no official communication so far.

Gupta, 53, a member of the secondary cadre known as Indian Foreign Service-B, was employed as a Urdu translator in the Indian High Commission. According to sources, she had been under observation and called back to India on the pretext of helping with the preparations of the SAARC summit.

She was reportedly held four days ago from her residence.

The espionage incident comes ahead of a likely meeting between Manmohan Singh and his Pakistani counterpart Yousuf Raza Gilani on the sidelines of the two-day SAARC summit beginning Wednesday.