The CBI, describes action to be taken under section 188 as:
In case the fugitive criminal is an Indian national, action can also be taken under Section 188 Cr.P.C., 1973 as if the offence has been committed at any place in India at which he may be found. The trial of such a fugitive criminal can only take place with the previous sanction of the Central Government.
They omitted the part about the inquiry of the offence which is contained in the CrPC as described below:
188.Offence committed outside India.- When an offence is committed outside India –
(a) by a citizen of India, whether on the high seas or elsewhere; or
(b) by a person, not being such citizen, on any ship or aircraft registered in India,
he may be dealt with in respect of such offence as if it had been committed at any place within India at which he may be found:
Provided that, notwithstanding anything in any of the preceding sections of this Chapter, no such offence shall be inquired into or tried in India except with the previous sanction of the Central Government.
Please understand Section 4 of the CrPC as well:
Section 4 of the Indian Penal Code reads as under:-
4. Extension of Code to extra-territorial offences.-
The provisions of this Code apply also to any offence committed by
(1) any citizen of India in any place without and beyond India;
(2) any person on any ship or aircraft registered in India wherever it may be.
Explanation.In this section the word offence includes every act committed outside India which, if committed in India, would be punishable under this Code.
Illustration: A, who is a citizen of India, commits a murder in Uganda. He can be tried and convicted of murder in any place in India in which he may he found.
The CBI explains extradition at its website. Here is the link: