CILACAP, Indonesia -- Indonesia executed four drug traffickers on Friday and said it had not yet decided when 10 others convicted of drug crimes would be put to death.

Deputy Attorney-General Noor Rachmad said one Indonesian and three Nigerians were executed by firing squad not long after midnight local time.

The government had said earlier in the week that 14 people on death row, mostly foreigners, would be executed on the Nusa Kambangan prison island.

Those executed Friday were Indonesian Freddy Budiman and Nigerians Seck Osmane, Michael Titus and Humphrey Jefferson. The bodies of Osmane and Titus will be flown to their home country and Jefferson will be buried in Indonesia.

Relatives, rights groups and foreign governments had urged Indonesia to spare all 14 lives but it was unclear whether that had any influence on the decision to not carry out all the executions at once. Lawyers and rights groups had raised serious doubts about the legitimacy of the conviction of Jefferson as well as the convictions of an Indonesian woman and a Pakistani man.

It was the third set of executions under President Joko "Jokowi" Widodo who was elected in 2014 and campaigned on promises to improve human rights in Indonesia.

"It was not a pleasant thing but it was to implement the law," said Rachmad. "The executions are only aimed at halting drug crimes."

He said a decision about other executions would be announced at a later time.

A convoy of 17 ambulances, most carrying coffins, had arrived Thursday morning at the port town nearest Nusa Kambangan. Officials began tightening security at the prison several days ago, with more than 1,000 police sent to Cilacap, the port town, and the island.

Last year, Indonesia executed 14 people convicted of drug crimes, mostly foreigners, sparking an international outcry.

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Wright reported from Jakarta. Niniek Karmini and Ali Kotarumalos contributed.