Two tankers thought to be carrying exports of oil from Iraqi Kurdistan have made their way to Asia, according to ship tracking data, bringing the number of Kurdish oil-loaded tankers believed to have reached the region to four.

The shipments represent one portion of the oil Iraqi Kurdistan has exported from the Turkish port of Ceyhan since May in defiance of the federal government in Baghdad, which claims sole authority over the country’s natural resources.

The tankers United Emblem and United Dynamic arrived off Singapore fully laden over the last two weeks, according to data provided by tanker tracking website Marine Traffic. Earlier in October, they separately sailed east of Singapore where the data showed their speed slowed and their draft in the water subsequently lessened, usually signs that the oil onboard had been discharged. The final buyers of the oil are unknown.

Despite Baghdad’s objections, the Kurdistan Regional Government has determinedly increased its shipments of oil to international markets in an effort to gain more financial independence.

One tanker that left from Ceyhan was stranded off the coast of Morocco for months after Baghdad succeeded in blocking its sale to a local refinery. Another remains off the coast of Texas, the subject of a lawsuit in the U.S. Still, oil continues to flow from Ceyhan.

The KRG has often resorted to a complex system to disguise the destination of its crude, turning off ships’ satellites and transferring oil from one tanker to another in the middle of the ocean.