They were taken into custody as they were heading to destroy a bridge, the police said, adding four grenades were recovered from them.
The four, suspected to be members of the Al Qaeda, were identified as Riazuddin alias Papa, Kamiran alias Kamu, Abdul Rehman and Aziz Mubarak, the police said.
On Saturday they were produced before a court, which remanded them to police custody for four days.
During interrogation they said they were recruited more than two months ago by two men from an Arab country and given Rs 10,000 to purchase explosives.
Aziz told the police that he met the two Arabs to plan attacks at the Karachi airport hotel, where forces in the US-led coalition in Afghanistan were staying, a media report said.
There was no official comment on the arrest.
Jaish was allegedly involved in the attack on Indian Parliament last year. It is also linked to the murder of US journalist Daniel Pearl.